An asymmetric slotted antenna for WLAN and WiMAX applications is proposed in this letter. The single-layer antenna is composed of a rectangular ground plane embedded with an asymmetric slot, which can generate dual bands. Utilising a CPW (Coplanar Waveguide) feeding line with a protrudent line to the top and a cupped part at left, good impedance matching can be achieved in the two working bands conveniently. Measured results show that the proposed antenna can provide two separate impedance bandwidths of 1.07 GHz (2.98 to 4.05 GHz) and 0.88 GHz (5.13 GHz to 6.01 GHz), making it easy to cover the specification for WiMAX operation band (3.3 GHz to 3.7 GHz) and WLAN operation in the 5.2/5.8-GHz bands. In addition, a comparison between measured and simulated results demonstrates that two resonant bands exhibit the good radiation patterns with the peak antenna gains of 5.6 dBi and 3.9 dBi, respectively.