A design of two microstrip antennas with improved isolation and reduction of mutual coupling between them using metamaterial structure is introduced. The technique which is used to reduce the coupling is complementary split ring resonator (CSRR) loaded between the two microstrip patches. The proposed antenna is designed to operate at frequency of 28GHz. This structure is suitable to operate in 5G and mm-wave antenna systems. A significant improvement in coupling between antennas using metamaterial structure is obtained compared to EBG structures at the same frequency. The maximum isolation achieved by etching the CSRR on the ground of the proposed antenna and on a floated ground between the two patched is 36.2 dB. The distance from edgeto-edge of the patch antennas is 0.4 λ0. In addition to design and simulate the proposed antenna using CST program, it is also fabricated and measured. Good agreement is achieved between simulated and measured results.