In this letter, a coplanar waveguide (CPW) dual-band bandpass filter for WLAN and WiMAX applications is proposed. The dual-band response is achieved by etching two pairs of spiral-shaped defected ground structures (DGS) on the CPW ground planes, a rectangular gap and T-shaped slots on the center strip, and extending T-shaped slots forming U-shaped structures on the grounds. Measured results show passbands centered at 3.67 GHz and 5.82 GHz, with return loss better than 10 dB over 3.33–4.01 GHz and 5.55–6.08 GHz. Three transmission zeros are generated, one in each stopband adjacent to the passbands, providing sharp frequency selectivity.