This article reports a case of Fournier gangrene after transrectal biopsy of the prostate. A 69-year-old male patient was admitted to our hospital for dysuria. The preoperative diagnosis was bladder stones and suspicious prostate cancer. During the same time, the patient underwent transurethral holmium laser lithotripsy and transrectal prostate biopsy. Fournier gangrene occurred on the second day after the operation. After active treatment such as upgraded antibiotics and debridement of the scrotum and perineum, the condition was controlled. The perineal wound healed 2 months later without secondary suture. Perioperative transurethral examination should be avoided during transrectal prostate biopsy. To avoid delayed diagnosis and treatment, it is necessary to improve the understanding of postoperative complications of Fournier's gangrene.