This research presents a graphene-based three element linear array (GTELA) microstrip antenna with an octagonal shape for short-range terahertz (THz) wireless communication applications. The antenna utilizes a four-layer structure comprising a gold ground plate and patch, with quartz (SiO4) material serving as the substrate with a thickness of 140 mu m deposited on the gold ground plate. On this substrate, an octagonal three-element linear array patch made of gold is applied, and finally, a fourth layer of elliptical-shaped graphene, with a thickness of 10 nm, is deposited onto the gold patch plate. The GTELA antenna demonstrates good performance, with a reflection coefficient value of less than - 10 dB in the 0.285-0.535 THz range, resulting in a substantial 250 GHz bandwidth and the realized gain value is 5.25 dBi. Consequently, the GTELA antenna proves to be a promising candidate for multiple input multiple output (MIMO) communication setups. The configured GTELA enhances the overall performance of MIMO array antennas, especially quad-port (QP) configurations, where the THz GTELA antenna elements are organized orthogonally, accommodating four cells with cross-sectional area of 2155.71 x 2155.71 mu m2. The proposed THz MIMO array realizes a bandwidth of 260 GHz within 0.275 to 0.535 THz frequency range and maintains mutual coupling coefficient of below - 20 dB.