A printed monopole antenna with microstrip-fed Sierpinski fractal geometry for dual wide band application is presented. The operating bands are adjusted with the design of modified Sierpinski triangle (radiating patch), ground plane and scale factor used to create a fractal shape. The simulated - 10 dB (VSWR 2:1) reflection bandwidth for first resonant frequency is 60% (1.47 GHz- 2.7 GHz). It covers GPS, DCS-1800, PCS-1800, UMTS, IMT-2000, WiBRO (Wireless Broadband Internet Services) and WLAN bands. For second resonant frequency the band width is 8% (4.991HHz-5.4 GHz) and covers 5.2 GHz WLAN (802.11/ a). The radiation characteristics and gain of the modified Sierpinski fractal antenna are also presented and discussed. © 2010 IEEE.