A 29-years-old male patient presented with complaint of the small size of his left testicle. The physical examination revealed a normal right testicle with 15 cc volume, a small left testicle (5 cc) and a 4 cc mass under the left testicle, which was thought to be a spermatocele. Ultrasonographic imaging was performed and the mass was defined as a third testicle with a heterogenic epididymis. Scrotal magnetic resonance imaging (MRI) confirmed the diagnosis. An inguinal exploration was performed, which resulted in a left orchiectomy and biopsy of the superior left testicle. The pathologic examination revealed hyperplasia with microcystic changes in the orchiectomy specimen and severe hypospermatogenesis in the biopsy sample. There were no significant changes in semen analysis after the operation.