New design of a microstrip patch antenna with Twin Eleven shaped slot is presented that achieves a minimum impedance bandwidth of 37.931%. The Twin Eleven shaped slot increases the bandwidth and reduces the complication of design to a very high extent while compared to other slot geometries due to the similarity in the shape of slots that are made on the patch. The proposed antenna is designed for the 5 GHz ISM band and is designed and simulated by the electromagnetic simulation software HFSS. The VSWR curve and the radiation patterns are also demonstrated in this paper in which the importance is given to the antenna bandwidth. © 2013 IEEE.