TIMELY INFORMATION INSIDE

Global Dynamic Income Fund (CHW)

SEMIANNUAL REPORT APRIL 30, 2018

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TABLE OF CONTENTS

Letter to Shareholders1

The Calamos Closed-End Funds:
An Overview5

Investment Team Discussion6

Schedule of Investments10

Statement of Assets and Liabilities23

Statement of Operations24

Statements of Changes In Net Assets25

Statement of Cash Flows26

Notes to Financial Statements27

Financial Highlights35

Report of Independent Registered
Public Accounting Firm36

About Closed-End Funds37

Managed Distribution Policy38

Automatic Dividend Reinvestment Plan38

Experience and Foresight

About Calamos Investments

For over 40 years, we have helped investors like you manage and build wealth to meet their long-term individual objectives by working to capitalize on the opportunities of the evolving global marketplace. We launched our first mutual fund in 1985 and our first closed-end fund in 2002. Today, we manage six closed-end funds. Three are total-return oriented offerings, which seek current income, with increased emphasis on capital gains potential. Three are enhanced fixed income offerings, which pursue high current income from income and capital gains. Calamos Global Dynamic Income Fund (CHW) falls into this latter category. Please see page 5 for a more detailed overview of our closed-end offerings.

We are dedicated to helping our clients build and protect wealth. We understand when you entrust us with your assets, you also entrust us with your achievements, goals and aspirations. We believe we best honor this trust by making investment decisions guided by integrity, by discipline, and by our conscientious research.

We believe an active, risk-conscious approach is essential for wealth creation. In the 1970s, we pioneered strategies that seek to participate in equity market upside and mitigate some of the potential risks of equity market volatility. Our investment process seeks to manage risk at multiple levels and draws upon our experience investing through multiple market cycles.

We have a global perspective. We believe globalization offers tremendous opportunities for countries and companies all over the world. In our view, this creates significant opportunities for investors. In our U.S., global and international portfolios, we are seeking to capitalize on the potential growth of the global economy.

We believe there are opportunities in all markets. Our history traces back to the 1970s, a period of significant volatility and economic concerns. We have invested through multiple market cycles, each with its own challenges. Out of this experience comes our belief that the flipside of volatility is opportunity.

John P. calamos, sr.

Founder, Chairman
and Global Chief
Investment Officer

CALAMOS Global Dynamic Income Fund SEMIANNUAL REPORT   1

Dear Fellow Shareholder:

Welcome to your semiannual report for the six-month period ended April 30, 2018. In this report, you will find commentary from the Calamos portfolio management team, as well as a listing of portfolio holdings, financial statements and highlights, and detailed information about the performance and positioning of this Calamos Fund. I encourage you to review this information carefully.

Calamos Global Dynamic Income Fund (CHW) is an enhanced fixed income fund. We utilize dynamic asset allocation to pursue high current income, while also maintaining a focus on capital gains.

Distribution

During the period, the Fund provided a compelling monthly distribution of $0.0700 per share. We believe the Fund’s current annualized distribution rate, which was 9.15%* on a market price basis as of April 30, 2018, was very competitive, given the low interest rates in many segments of the bond market. In our view, the Fund’s distributions illustrate the benefits of a multi-asset class approach and flexible allocation strategy.

We understand that many closed-end fund investors seek steady, predictable distributions instead of distributions that fluctuate. Therefore, this Fund has a managed distribution policy. As part of this policy, we aim to keep distributions consistent from month to month, and at a level that we believe can be sustained over the long term. In setting the Fund’s distribution rate, the investment management team and the Fund’s Board of Trustees consider the interest rate, market and economic environment. We also factor in our assessment of individual securities and asset classes.

*Current Annualized Distribution Rate is the Fund’s most recent distribution, expressed as an annualized percentage of the Fund’s current market price per share. The Fund’s 4/30/18 distribution was $0.0700 per share. Based on our current estimates, we anticipate that approximately $0.0700 is paid from ordinary income or capital gains and that approximately $0.0000 represents a return of capital. Estimates are calculated on a tax basis rather than on a generally accepted accounting principles (GAAP) basis, but should not be used for tax reporting purposes. Distributions are subject to re-characterization for tax purposes after the end of the fiscal year. This information is not legal or tax advice. Consult a professional regarding your specific legal or tax matters. Under the Fund’s managed distribution policy, distributions paid to common shareholders may include net investment income, net realized short-term capital gains and return of capital. When the net investment income and net realized short-term capital gains are not sufficient, a portion of the distribution will be a return of capital. In addition, a limited number of distributions per calendar year may include net realized long-term capital gains. The distribution rate may vary.

2   CALAMOS Global Dynamic Income Fund SEMIANNUAL REPORT

Market Review

The semiannual period was characterized by two distinct environments, and in particular, the return of volatility to the markets in January. Through the final months of 2017, U.S. and global stock markets advanced briskly as investors focused on positive global economic growth trends, low inflation, deregulation and anticipation of tax reform. However, the climate changed in 2018. Although economic fundamentals remained compelling around the world, market participants became distracted by the potential for more Federal Reserve hikes and rising inflation. After many years of subdued volatility and record-low interest rates, the stock market became increasingly turbulent as the period progressed.¹ Fixed income asset classes also encountered headwinds.^2,3 Convertible securities, in contrast, demonstrated resilience in the choppy markets, illustrating the potential benefits of their unique structural characteristics.⁴

Outlook

We believe positive economic conditions and corporate fundamentals can support a continuation of the bull market in stocks, as well as opportunities across asset classes. Global economic data is positive on the whole. GDP growth has continued at a good pace in the U.S., and tax reform and deregulation can provide further catalysts from here. The U.S. consumer has benefitted from job growth, wage gains and rising housing values. Corporate fundamentals—including earnings, sales and revenue growth—are very strong. Inflation has increased but is coming off historically low levels and remains contained. As economic growth continues, we expect the Fed to maintain its course of raising short-term interest rates gradually. This slow pace, combined with conditions in the broader global bond markets, may help keep longer-term U.S. rates from rising unchecked.

Although economic conditions are favorable, managing volatility will be key to succeeding in this environment. Evolving trade policies, uncertainties around North Korea and Russia, and U.S. mid-term elections will likely contribute to short-term market disruptions over coming months. An extended trade war could be an economic headwind, but we do not see this as the probable outcome. We are hopeful that moves by the U.S. over recent months can set the stage for negotiations that lead to freer and fairer trade over the long term.

Thoughts for Investors

The stock market’s gyrations, rising interest rates and signs of inflation have unsettled many investors. However, if we look back over longer periods, the environment we are seeing today is actually more normal than those of the past few years when volatility, interest rates and inflation were exceptionally low.

CALAMOS Global Dynamic Income Fund SEMIANNUAL REPORT   3

In this more typical environment, we believe there are many opportunities for active and risk-aware approaches. Our investment professionals remain vigilant to avoiding unintended risks in the Fund. They are also working together to turn short-term volatility into opportunities for the shareholders in the Fund. Our ability to respond to changing market conditions will be especially important given the many crosscurrents we see.

In Closing

More than 40 years of experience supports my belief that investors are best served by maintaining a long-term approach. Fast moving markets can increase the temptation to make short-term moves. But as I’ve noted in the past, there’s no way to predict with certainty the daily twists and turns. Far too often, trying to time the ups and downs leaves investors capturing the downside and missing the upside. Instead, I encourage you to work with your financial advisor to create a well-diversified asset allocation that meets your financial goals. By blending an array of funds—including stocks, convertibles, alternative and fixed income strategies—investors may be better positioned to achieve their long-term goals.

I am confident that the Fund is well equipped to navigate the course ahead. Since our earliest days as an asset manager, we have sought to provide innovative strategies for managing risk and enhancing returns. While others may be discouraged by these more choppy markets, we welcome the return of more normal levels of volatility and the opportunities it will bring for our active approach.

I hope that you find this report informative, and I invite you to visit our website www.calamos.com for additional resources. All of us at Calamos Investments thank you for your continued trust. It is truly an honor to help you achieve your financial goals.

Sincerely,

John P. Calamos, Sr.

Founder, Chairman and Global Chief Investment Officer

4   CALAMOS Global Dynamic Income Fund SEMIANNUAL REPORT

CALAMOS Global Dynamic Income Fund SEMIANNUAL REPORT   5

In our closed-end funds, we draw upon decades of investment experience, including a long history of opportunistically blending asset classes in an attempt to capture upside potential while seeking to manage downside risk. We launched our first closed-end fund in 2002.

Closed-end funds are long-term investments. Most focus on providing monthly distributions, but there are important differences among individual closed-end funds. Calamos closed-end funds can be grouped into multiple categories that seek to produce income while offering exposure to various asset classes and sectors.

Our Managed Distribution Policy

Closed-end fund investors often seek a steady stream of income. Recognizing this important need, Calamos closed-end funds adhere to a managed distribution policy in which we aim to provide consistent monthly distributions through the disbursement of the following:

•Net investment income

•Net realized short-term capital gains

•Net realized long-term capital gains

•And, if necessary, return of capital

We set distributions at levels that we believe are sustainable for the long term. Our team focuses on delivering an attractive monthly distribution, while maintaining a long-term emphasis on risk management. The level of the funds’ distributions can be greatly influenced by market conditions, including the interest rate environment, the individual performance of securities held by the funds, our view of retaining leverage, fund tax considerations, and regulatory requirements.

You should not draw any conclusions about the Fund’s investment performance from the amount of this distribution or from the terms of the Fund’s plan. The Fund’s Board of Trustees may amend or terminate the managed distribution policy at any time without prior notice to the Fund’s shareholders.

For more information about any Calamos closed-end funds, we encourage you to contact your financial advisor or Calamos Investments at 800.582.6959 (Monday through Friday from 8:00 a.m. to 6:00 p.m., Central Time). You can also visit us at www.calamos.com.

6   CALAMOS Global Dynamic Income Fund SEMIANNUAL REPORT

TOTAL RETURN* AS OF 4/30/18

SECTOR WEIGHTINGS

Sector Weightings are based on managed assets and may vary over time. Sector Weightings exclude any government/sovereign bonds or options on broad market indexes the Fund may hold.

Global Dynamic Income Fund (CHW)

INVESTMENT TEAM DISCUSSION

Please discuss the Fund’s strategy and role within an asset allocation framework.

Calamos Global Dynamic Income Fund (CHW) is a globally enhanced fixed-income offering that seeks to provide an attractive monthly distribution with a secondary objective of capital appreciation. We believe it offers a diversified way to participate in the long-term potential of global markets.

In this portfolio, we draw upon our team’s wide-ranging experience in an array of asset classes. We utilize what we believe is a highly flexible approach investing in equities, convertible securities and high yield securities. We also can employ alternative strategies such as covered call writing and convertible arbitrage. Through covered call writing, we seek to generate income by selling (“writing”) options on market indexes. In the convertible arbitrage strategy, we invest in convertible securities and short sell the convertibles’ underlying equities to generate income and hedge against risk.

We believe that this broad mandate enhances our ability to capitalize on market volatility, manage potential downside risks and generate more income versus traditional fixed income funds. The allocation to asset classes and strategies is dynamic, and reflects our view of the economic landscape and the potential of individual securities. By combining asset classes and strategies, we believe that we are well positioned to generate income and capital gains. The broader range of security types also provides us with increased opportunities to manage the risk/reward characteristics of the portfolio over full market cycles. For the period, our exposure to the equity markets was beneficial to the overall performance of the Fund.

We invest in both U.S. and non-U.S. companies, with at least 50% of assets invested in non-U.S. companies. We emphasize companies with reliable debt servicing, respectable balance sheets and sustainable prospects for growth. Regardless of a company’s country of domicile, we favor companies with geographically diversified revenue streams and global business strategies.

How did the Fund perform over the reporting period?

The Fund returned 1.72% on a net asset value (NAV) basis for the six-month period ended April 30, 2018. On a market price basis, the Fund returned 5.25%. For the sake of comparison to the broader global markets, the MSCI EAFE Index returned 3.67%, the MSCI World Index returned 3.68%, and the S&P 500 Index gained 3.82% during the period.

At the end of the reporting period, the Fund’s shares traded at a 2.57% premium to NAV.

CALAMOS Global Dynamic Income Fund SEMIANNUAL REPORT   7

SINCE INCEPTION MARKET PRICE AND NAV HISTORY THROUGH 4/30/18

Performance data quoted represents past performance, which is no guarantee of future results. Current performance may be lower or higher than the performance quoted. The principal value of an investment will fluctuate so that your shares, when sold, may be worth more or less than their original cost. Returns at NAV reflect the deduction of the Fund’s management fee, debt leverage costs and all other applicable fees and expenses. You can obtain performance data current to the most recent month end by visiting www.calamos.com.

How do NAV and market price return differ?

Closed-end funds trade on exchanges, where the price of shares may be driven by factors other than the value of the underlying securities. The price of a share in the market is called market value. Market price may be influenced by factors unrelated to the performance of the fund’s holdings, such as general market sentiment or future expectation. A fund’s NAV return measures the actual return of the individual securities in the portfolio, less fund expenses. It also measures how a manager was able to capitalize on market opportunities. Because we believe closed-end funds are best utilized long-term within asset allocations, we believe that NAV return is the better measure of a fund’s performance. However, when managing the fund, we strongly consider actions and policies that we believe will optimize its overall price performance and returns based on market price.

Please discuss the Fund’s distributions during the six-month period.

We employ a managed distribution policy* within this Fund with the goal of providing shareholders a consistent distribution stream. In each month of the period, the Fund distributed $0.0700 per share, resulting in a current annualized distribution rate of 9.15% of market price as of April 30, 2018.

We believe that both the Fund’s distribution rate and level remained attractive and competitive, as low interest rates limited yield opportunities in much of the marketplace. For example, as of April 30, 2018, the dividend yield of S&P 500 Index stocks averaged approximately 2.11%.† Yields also were still relatively low within the U.S. government bond market, with the 10-year U.S. Treasury and 30-year U.S. Treasury yielding 2.95% and 3.11%, respectively.‡

*Under the Fund’s managed distribution policy, distributions paid to common shareholders may include net investment income, net realized short-term capital gains and return of capital. When the net investment income and net realized short-term capital gains are not sufficient, a portion of the distribution will be a return of capital. In addition, a limited number of distributions per calendar year may include net realized long-term capital gains. The distribution rate may vary.

†Source: Calamos Investments

‡Source: U.S. Department of the Treasury

8   CALAMOS Global Dynamic Income Fund SEMIANNUAL REPORT

What factors influenced performance over the reporting period?

The Fund has the ability to invest in a range of strategies including convertible securities, high yield, U.S. equities, international equities, as well as convertible arbitrage. This enables us to participate in a myriad of opportunities on behalf of our shareholders. Given this flexibility, we were able to maintain our exposure to the equity markets in part through our convertible holdings, which allowed us to participate in the general upward trajectory of equities and mitigate the volatility that returned to the markets in dramatic fashion.

The Fund’s attractive share price relative to the NAV earlier in the period served as an enticement to many investors and enhanced price performance.

The Fund’s U.S. equity sleeve outperformed relative to the S&P 500 Index, as selection in consumer staples, specifically selection and an underweight in household products, outperformed relative to the index. In addition, our selection in financials, namely in investment banking and brokerage, was helpful.

Conversely, our selection in information technology, particularly selection in communications equipment, impeded performance relative to the index. In addition, our selection in consumer discretionary, namely internet and direct marketing retail, was not helpful.

The Fund’s global equity sleeve underperformed relative to the MSCI World Index. Our selection in materials, namely an overweight in specialty chemicals, weighed on performance. In addition our selection in consumer discretionary, specifically in internet and direct marketing retail, also held back results.

Conversely, our lack of exposure to household products in consumer staples was helpful. Our selection in the oil and gas exploration and production area of energy also proved beneficial.

Our holdings in the United States helped performance relative to the MSCI Index. However, our EMEA holdings were a disappointing offset.

The Fund’s international sleeve underperformed relative to the MSCI EAFE Index. Selection in health care with respect to biotechnology impeded performance relative to the MSCI EAFE Index. In addition, our selection in industrials, notably an overweight and selection in industrial conglomerates, hindered return. Our overweight to the United States relative to the index was also not helpful.

Conversely, our selection in financials (specifically financial exchanges and data) was beneficial relative to the index. In addition, our overweight to energy, namely the allocation in oil and gas exploration and production, was helpful. Our selection in Europe was also positive.

Convertible arbitrage generally entails owning a convertible bond long and shorting its underlying stock. It is employed as a strategy to enhance returns. The convertible arbitrage sleeve performed positively during the reporting period and contributed to the overall Fund return. The increase in volatility observed during the period was supportive to the Fund, providing opportunities to rebalance our hedges. The Federal Reserve hiked its fed funds rate by 25 basis points twice during the period to 1.75%. This was supportive to the interest carry (interest earned) on our convertible arbitrage short equity positions. At the same time, rising interest rates presented a challenge to convertible bond arbitrage as the bond value portion of the convertible declined. While high yield credit spreads** narrowed 21 basis points during the period to 387 basis points above Treasuries (JPMorgan), the narrower spreads were not enough to offset the impact from rising interest rates.

**The difference between the yield of two bonds with differing ratings. The narrowing of high yield bond spreads would imply that the price of those bonds rose.

CALAMOS Global Dynamic Income Fund SEMIANNUAL REPORT   9

How is the Fund positioned?

We continue to find opportunities across asset classes, maintaining a preference for larger-cap growth-oriented companies with global presence and geographically diversified revenue streams. We believe that such companies should be particularly well positioned to capitalize on the global growth trends we see. In keeping with an emphasis on risk management, we focus on companies that we believe have respectable balance sheets, solid free cash flows, good prospects for sustainable growth as a result of global economic synchronization, and reliable debt servicing.

The portfolio’s largest allocations—in absolute terms—are found in the information technology, consumer discretionary and financials sectors. We believe that many information technology companies offer compelling fundamentals and participation in secular growth trends. In regard to consumer discretionary, we believe that companies in the sector should benefit from improving economic conditions highlighted by higher employment, improved consumer sentiment and relatively low interest rates. In addition, we believe that our exposure to financial companies will do well in a rising interest rate, lower regulatory and reflationary environment. Conversely, we are maintaining relatively low exposures to utilities, which we believe are fully valued at this point in the cycle.

As noted, we pursue a risk-managed approach to total return. This said, the Fund’s portfolio includes a blend of high yield and investment-grade credits. We take a very selective approach to CCC-rated credits. Given our view that economic growth should be closely monitored, we believe it is important to favor companies that offer the best prospects for reliable debt servicing.

We believe this environment is conducive to the prudent use of leverage as a means of enhancing total return and supporting the fund’s distribution rate. In spite of a cost increase due to rising interest rates, our use of leverage over the period enjoyed a favorable reinvestment dynamic. As of April 30, 2018, our amount of leveraged assets was approximately 34%.

What are your closing thoughts for Fund shareholders?

Given our outlook for a continued period of economic growth, at least in the short term, we are favoring quality growth companies over cyclicals. Favorable factors within the U.S. include solid job creation, low interest rates, range-bound energy prices, increasing consumer confidence and limited inflationary pressures. We are emphasizing investments in companies with solid cash-flow generation and stronger balance sheets. From a thematic and sector perspective, we see opportunities in the technology sector, consumer discretionary companies tied to global consumption, and companies positioned to benefit from improving fundamentals. We are also optimistic about financials, as we believe that many financial companies are favorably valued and positioned to grow revenues in a rising interest rate environment with less regulations. However, we are cautious about companies in the consumer staples sector. We believe they may be fully valued as investors are attracted to those stocks for income rather than growth. We are selective regarding the health care sector, favoring those companies that are more product-growth oriented versus price driven to achieve earning growth. We believe our active, risk-managed investment approach positions us to take advantage of volatility as well as opportunities in global equities and convertible securities.

It appears that fiscal policy and geopolitical concerns are likely to remain a focal point of market anxiety. However, we think that the Fed will try to be accommodative toward fiscal growth. We also anticipate government policies being more business friendly. In our view, equities continue to offer compelling risk/reward characteristics, and we are seeking companies with attractively valued fundamentals. That said, risk assessment via an actively managed portfolio is imperative during times of volatility to optimize returns.