Here, a near-zero permittivity (e) and permeability (μ) metamaterial superstrate is presented as a decoupling structure for a multiple-input-multiple-output (MIMO) antenna. The proposed design offers peak isolation of 41 dB with reduced edge separation of 0.042γo at the resonating frequency. To verify the simulation results, the prototype of the proposed superstrate and antenna is fabricated and tested. The two-element MIMO antenna has -10 dB impedance band of 5.5-5.92 GHz with a peak measured gain of 7.41 dBi and efficiency above 78%. The measurement results ensure an isolation enhancement of 30 dB with a correlation coefficient of <0.26 within the operating band. The proposed method offers a good design technique for high gain and a closely packed MIMO antenna system for WLAN applications. © The Institution of Engineering and Technology 2020.