A novel simple multi resonant comb-shaped patch microstrip antenna for multi functional wireless communications bands is presented and simulated. This new structure is fed by a microstrip line. A parametric study of the multi resonant comb-shaped patch antenna is presented and effect of the size of the slots on return loss, radiation patterns and gain has been investigated and the results are discussed. This antenna generates eleven resonant frequencies in the frequency range of 0.5 GHz to 6 GHz and has good radiation characteristics with less than 10-dB return loss at resonant frequencies. Due to its simple structure, it could be widely used in several applications especially in the WLAN/WiMAX, portable wireless devices.