Transplantation of human allogeneic induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) is a new, promising treatment for severe heart failure. However, immunorejection is a significant concern in allogeneic hiPSC-CM transplantation, requiring the administration of several immunosuppressive agents. An appropriate protocol for the administration of immunosuppressants may substantially affect the efficacy of hiPSC-CM transplantation in case of heart failure owing to allogeneic transplantation. In this study, we investigated the effect of immunosuppressant administration duration on the efficacy and safety of allogenic hiPSC-CM patch transplantation. We used a rat model of myocardial infarction to evaluate cardiac function using echocardiography six months after the transplantation of hiPSC-CM patches with immunosuppressant administration for either two or four months and compared them to control rats (sham operation, no immunosuppressant administration). Histological analysis performed at 6 months after hiPSC-CM patch transplantation revealed significant improvement in cardiac function in immunosuppressant-treated rats compared with those in the control group. Moreover, fibrosis and cardiomyocyte size was significantly reduced and the number of structurally mature blood vessels was significantly increased in the immunosuppressant-treated rats compared to control rats. However, there were no significant differences between the two immunosuppressant-treated groups. Our results show that prolonged administration of immunosuppressive agents did not enhance the effectiveness of hiPSC-CM patch transplantation, and therefore, highlight the importance of an appropriate immunological regimen for the clinical application of such transplantation.