In this paper, a compact circular UWB (ultra-wideband) antenna with WLAN 802.11a/n band (5.15∼5.825 GHz) rejection characteristic is proposed for the mobile applications. The proposed UWB antenna was compact enough to be loaded into a mobile handset. The performance of the suggested antenna is mostly dependent on the gap between circular radiator and the ground plane. In order to have the band notched operation, the CSRR (complementary split ring resonator) is etched inside the circular patch of the UWB antenna. MWS (Microwave Studio) of CST company was utilized in the design stage. The antenna was constructed on a substrate, Rogers 4003, with the thickness of 0.8 mm and relative permittivity of 3.38. A size of substrate is 24 × 37.5 mm2 and a radius of circular radiator is 5 mm long. The proposed antenna covers the frequency band from 3.2 to 10.6GHz (S11 ≤ 10dB), and the band rejection occurs about 5.7 GHz band. A simulation shows the maximum gain of 5.2 dBi, and radiation pattern is nearly omni-directional over the entire -10 dB return loss bandwidth. It also represents the group delay below 1nsec over UWB communication band (3.2GHz∼10.6GHz) except WLAN band. Based on the experimental results, the proposed antenna could be a good candidate for the handheld mobile handsets.