The Sierpinski fractal antenna has been analyzed parametrically, and observed how its characteristics changing with the variation of its different parameters. The input return loss and input impedance have log periodic behavior that characterizes the sierpinski monopole antenna as fractal geometry. The band spacing and impedance matching have been improved by using different scale factor and feeding methods. Sierpinski monopole antenna for WLAN bands (2.4GHz and 5GHz) has been designed and simulated using Ansoft Hfss.The operating frequencies of the proposed designs match with IEEE802.11b (2.45GHz) and IEEE802.11a (5.20 GHz and 5.775GHz) standards which would allow WLAN operation. Key words— Sierpinski gasket, Fractal, Input impedance, Gain, Multiband, Input Return loss.