In a wireless communication system, a microstrip patch antenna is gaining importance as a most powerful technology trend and it is applicable for the development of low-cost, minimal-weight, low-profile and high-performance antenna. This paper presents the design and the analysis of 1 × 2, 1 × 4 and 2 × 8 rectangular microstrip patch antenna (RMPA) arrays based on the photonic crystals for improved gain performance and high radiation characteristics compared to ones that are designed based on the homogeneous substrate in the frequency range of 0.25 - 0.55 THz. The design of the proposed antenna arrays based on the photonic band gap (PBG) and the homogeneous substrate structures is made by using the designed single-element RMPA as the basic building element, and then, they were fed by the parallel feeding structure. The designed antenna arrays were simulated using CST Microwave Studio software and validated with the aid of Ansoft HFSS simulator. For high radiation characteristics, the proposed antenna arrays resonated around 0.35 THz which is a low loss frequency window in the terahertz band. The main results showed that the designed antenna arrays based on the PBG substrate structure outperform the antenna arrays based on the homogeneous substrate in terms of return loss, bandwidth, gain and directivity. The best directivity was achieved by the 2 × 8 RMPA array of 17.40 dBi, whereas the 1 × 4, 1 × 2 RMPA arrays and single-element RMPA achieved the directivity of 13.54 dBi, 9.87dBi and 7.76 dBi, respectively. Hence, the designed antenna arrays can be used for medical imaging, threat detection and wireless surveillance communication.