A 46-year-old male patient visited our hospital with the chief complaint of a right scrotal swelling and pain. The enlarged scrotum was 8 cm in diameter with redness of the skin of the right scrotum. There was a firm mass in the scrotum with marked tenderness. The patient's body temperature was 38.0C, and blood tests showed increased inflammatory markers. The results of computed tomography and magnetic resonance imaging showed that the enlarged scrotum was filled with gas and there was a mass partially composed of fat inside it. The patient was treated with antibiotics, but the fever persisted and the inflammatory markers further increased. The size of the right scrotum gradually increased. A right high inguinal orchiectomy was performed to control the inflammation and makea diagnosis. Thehistopathological diagnosis was necrosis of seminoma, and culture of thene crotic tissuewas positivefor Clostridium. Thepre sent caseappe ars to bethefirst caseof a testicular tumor associated with acute scrotum due to tumor growth, necrosis and infection caused by gas-producing bacteria.