Pneumocystis jirovecii pneumonia (PJP) and cytomegalovirus (CMV) colitis are opportunistic infections that occur during immunosuppressive treatments for ulcerative colitis (UC). The prognosis of PJP and CMV colitis is very poor. We herein report a rare case of a 74-year-old UC patient with PJP and CMV colitis that was successfully treated with intensive therapy. PJP progresses rapidly, so the timing and choice of treatment are critical. Furthermore, a literature review of similar cases suggested that prophylactic therapy for opportunistic infections might be important, especially in the elderly. This case will serve as a reference for successful treatment in future cases.