This letter presents a novel frequency-reconfigurable folded slot antenna that could operate in two modes. Both modes have two resonant frequencies. The first mode resonant frequencies are at 3.4 and 5.27 GHz, and it can be used in WLAN band (5.15-5.35 GHz) and WiMAX band (3.40-3.69 GHz). The second mode operating frequencies are at 2.42 and 5.79 GHz, and they can be used in WLAN band (5.725-5.875 GHz) and Bluetooth band (2.40-2.484 GHz). The simulated results both for the return loss and peak gain agree with the measurements. Both the slot and arms of the proposed folded slot antenna are used to result in a resonant frequency, respectively. The advantage of this design is that the antenna is easy to fabricate, and this antenna could work without a complex bias network and a dc blocking capacitor.