In this study, a 4-port MIMO antenna structure with multiple inputs, and multiple outputs is presented. The proposed structure is intended to run at 28 GHz. This is an indication of the 5G communication systems' higher band. A microstrip feed line with a permittivity of 3.38, tan δ = 0.002, and a height of 0.213 mm is positioned on the top side of a Rogers RO 4003C substrate in the suggested antenna. A full ground plan with a rectangular slot is located on the second side. The 24 ×24 mm2 proposed antenna has a bandwidth of 5 GHz (17.54%) and operates in the 26 GHz to 31 GHz frequency range. The four elements MIMO antenna are positioned perpendicularly to improve diversity and isolation among the radiators. It achieves a peak gain of around 5 dB, which occurs at a frequency of 28 GHz. This antenna is fabricated and measured. The proposed design is employed in 5G applications, according to the results of the simulation and measurement, which demonstrate a satisfactory match with the target band.