This study aims to reduce the mutual coupling and envelope correlation coefficient (ECC) parameters of massive MIMO antennas. This parameter is important to support the performance of MIMO antennas in increasing high-speed data transmission. The observation of this study was carried out at the C-Band 3.5 GHz frequency as one of the 5G frequency bands under 6 GHz. The study used a massive MIMO 64 element antenna design with the addition of a specially designed Uni-planar Compact EBG (UC-EBG) surrounding the antenna element. Simulation and measurement results are compared with conventional MIMO antenna performance (without UC-EBG). Simulation results and antenna measurements show that the addition of the UC-EBG structure has succeeded in reducing the mutual coupling by 1.23 dB and improve the ECC parameter by 0.61. In addition, the UC-EBG structure can improve the performance of return loss and massive MIMO antenna VSWR