A 54-year-old male patient presented with pneumaturia. Right scrotal swelling was observed. CT showed an intrascrotal abscess with gas formation. MRI showed a fistula extending from the sigmoid colon to the seminal vesicles. Since there are many diverticula in the sigmoid colon, an abscess caused by diverticulitis may have formed a fistula. The scrotal abscess was drained; however, the pus discharge did not decrease. A colostomy was then performed, and the scrotal infection rapidly improved. Sigmoidectomy and fistula transection were performed 11 months after the colostomy. Prompt diagnosis of a sigmoid coloseminal fistula using imaging has led to optimal treatment.