In present scenario dual band high gain microstrip patch antennas are very much desirable in view of 5G mobile communication implementation in near future, So, this paper presents a new dual band Circularly Polarized (CP) patch antenna operating in 5G band. A rectangular slot at angle 45 0 is used for the design of this compact dual band CP patch antenna. The proposed antenna can operate at 28 GHz and 38 GHz having bandwidth 900 MHz and 1.3 GHz, respectively, which are useful in mobile 5G communication and multimedia wireless systems. Axial Ratio Band Width (ARBW) is 210 MHz at 28 GHz and 300 MHz at38GHz.The gain of the proposed antenna is 7.5 dBi and 7.7 dBi at 28 GHz and 38 GHz, respectively. The proposed dual band microstrip patch antenna has been simulated, optimized and miniaturized by using EM simulator software HFSS.