A 30-year-old man who complained of sudden right scrotal pain visited our clinic. Physical examination revealed a palpable mass with tenderness on his right testis. An emergent operation was performed for acute scrotum. The intraoperative findings showed a small, white, elastic solid, a smooth surface tumor that originated from the tunica albuginea of the right testis. It seemed to be benign macroscopically and partial orchiectomy was performed. Soon after surgery, the pain disappeared. Pathohistological examination revealed an adenomatoid tumor of the testis which originated from the rete testis. Adenomatoid tumor of the testis is a rare benign tumor. In general, it can be diagnosed by observation of an incidental, pain-free and small palpable mass of the testis. Therefore, we should be aware that an adenomatoid tumor of the testis can be one of the differential diagnoses of acute scrotum.