Presented work describes the symmetrical quad-element Multiple-Input Multiple-Output (MIMO) antenna operating at 28 GHz for Fifth generation (5G) millimeter-wave (mm-wave) spectrum. The core of this antenna system features a stepped-shaped patch radiator precisely tuned to 28 GHz, effectively broadening its resonance across the desired operational frequency band. To improve isolation, an Isolating Metallic Sheet (IMS) is precisely placed between the patch radiators of projected antenna. Rogers RT5880 substrate is used to fabricate with dimensions of 20.48 × 20.48 mm2, thickness of 1.6 mm, and dielectric constant of 2.2. Both simulationand measurement outcomesindicate that the antenna has a bandwidth of 7.13 GHz, covering frequencies ranging from 25.21 GHz to 32.34 GHz, for a fractional bandwidth of 24.78 %. Key antenna performance measurements include a peak amplitude of up to 53 dB and a significant port-to-port isolation of more than 20 dB. Ithasbeen carefully examined revealing a minimum channel capacity loss of 0.135 bits/s/Hz, a mean effectivegain of −3 dB, a diversity gain of around 10 dB, a total active reflection coefficient of −10 dB, and an envelope correlation coefficient of less than 0.005. Presentedantenna meets industrial requirementsfor high-speed mm-wave communications in 28 GHz 5G networks.