A CPW-fed U-Shaped antenna with defected ground plane for WiMAX and UWB applications is presented in this paper. The antenna consists of a U-shaped patch, defected ground plane and a coplanar waveguide (CPW) feed line. The proposed antenna is designed on FR4 epoxy substrate. The antenna has a dimension of 24.5× 16× 1.6 mm3 with a loss tangent of 0.002 and dielectric constant 4.4 and it is optimized using IE3D simulator. The proposed antenna has an impedance bandwidth of (3.1 –10.6) GHz and (VSWR <2). The simulation results show that the antenna has UWB characteristics and is resonating at a frequency at 3.50 GHz. The antenna characteristics also covers WiMAX (3.2–3.8 GHz) application.