In this work, tri resonance multi slot microstrip patch antenna which operates at three center frequencies of 11 GHz, 11.9 GHz, 15.7 GHz is designed and simulated. As a commercial simulation tool, Sonnet Suites, a planar 3D electromagnetic simulator was used. Details of the simulation results are presented and discussed. As a result, an input match of -6.88 dB at the resonance frequency of 11 GHz, an input match of -37.12 dB at the resonance frequency of 11.9 GHz, an input match of -29.49 dB at the resonance frequency of 15.7 GHz were observed. The gain was observed as 8.25 dB at 11 GHz and 4.82 dB at 11.9 GHz. Also, the gain was observed as 7.07 dB at 15.7 GHz. The patch has several symmetric slots and it’s well known that slots change the current distribution of the patch antenna.