A proximity-coupled graphene patch-based full-duplex antenna is proposed for terahertz (THz) applications. The antenna provides a 10 dB impedance bandwidth of 6.06% (1.76 − 1.87 THz). The input ports of the proposed design are isolated from each other by −25 dB. The aspect ratio of the graphene-based radiating patch and the physical parameters of the antenna is selected for obtaining the single-mode operation. The dimensions (length and width of graphene) of the proposed antenna have been opted to operate in two higher-order orthogonal modes, and these modes remain intrinsically isolated. The utilization of the graphene material provides flexibility in tuning the antenna response. Graphene-based patch exhibits good electrical conductivity, electrical conductance controllability, and plasmon properties. The graphene-based antennas perform better than their metallic counterparts, especially in the THz frequency range. The radiation properties of the graphene material are more prominent due to no-ohmic losses. Moreover, its chemical potential may be altered by applying a bias voltage to its surface conductivity, which modifies the surface impedance value of graphene. Therefore, with a small footprint, graphene acts as an excellent radiator at extremely high frequencies.