This paper proposes a new quad-port Multiple-Input-Multiple-Output antenna with a unique Maze structure Epsilon Negative (ENG) Metamaterial superstrate for 5G NR C-band applications. The suggested 2x2 MIMO antenna has four microstrip antennas with a C-shaped stub inside the slot arranged orthogonally on a FR4 substrate. The overall dimension of the proposed 2x2 MIMO antenna is 0.62λ0 x 0.62λ0 x 0.02λ0, where λ0 is the free space wavelength at 3.7 GHz. The proposed MIMO antenna has excellent impedance matching over a bandwidth of 32% (3.2 GHz–4.4 GHz). The proposed antenna incorporates a superstrate layer composed of modified maze-structured metamaterial elements with a unit cell size of 0.16λ0 x 0.16λ0 x 0.02λ0 on a single-layer FR4 substrate to enhance the antenna's gain, improve isolation properties, and achieve size reduction. By strategically placing the metamaterial superstrate, it reduces the mutual coupling between the antennas and enhances peak isolation of < −30 dB. In order to accomplish the goals of isolation and gain improvement, the metamaterial superstrate is positioned 10.5 mm (0.13λ0) above the MIMO components. Furthermore, it attains a 3.54 dB peak realized gain, which is enhanced by 162% across the frequency ranges, and the overall size of the MIMO antenna is reduced to approximately 17%. Adequate values for factors such as the diversity gain, envelope correlation coefficient, channel capacity loss, and total active reflection coefficient are also determined for the MIMO antenna performance. The design prototype of the proposed antenna is built and verified by measurements that reveal a strong correlation with the simulation's output.