A dual band microstrip antenna for WIMAX and WLAN applications is analyzed and presented in this paper. The proposed antenna has semicircular slot in patch and Defected Ground Structure (DGS) technique for the improvement of its bandwidth and gain. Computer Simulation Technology (CST) software is used to design and simulate the performance characteristics. The proposed antenna has the dimensions as 28 × 26.6 𝑚𝑚 2 . The fabricated antenna provides a good reflection coefficient of -48 dB and -44.5 dB at a center frequency of 3.4 GHz and 5.5 GHz. Gain achieved by the antenna is 2.72 dB and 3.87 dB for WLAN and WIMAX application. Good agreements have been found between simulated and measured results. These results confirm that the fabricated antenna is very promising for WLAN and WIMAX applications.