Fournier's gangrene (FG) is known as a rapidly progressing necrotizing fasciitis arising from genitourinary and colorectal infections. Misdiagnoses have occurred often because the initial presentation varies and is unclear. We report a case of FG in a 59-year-old man who had undergone a living donor liver transplant. He was in the maintenance phase of immunosuppressant treatment. FG occurred rapidly without symptoms and required prompt and aggressive debridement. Computed tomography demonstrated a small air density in his left testis. Treatment with hyperbaric oxygen therapy followed by intra- operative Gram's staining navigated debridement was additionally performed with general systematic anti-biological therapy and successfully cured the patient. Extra caution should be paid to patients who are maintained on immunosuppressants. Earlier detection and intervention will reduce the rate of mortality to a minimum.