A 41-year-old man presented a bean sized, solid, painless left scrotal mass he'd had for 10 years. The mass was well demarcated and it showed homogeneous echogenecity on ultrasonography. Simple mass excision was performed and the specimen revealed a relatively well circumscribed mass lesion composed of dilated tubules with flattened lining cells. A focal infiltration to the seminiferous tubule and involvement of the biopsy margins were observed. The tubules had a positive reaction to the calretinin and anti-mesothelial antibody on immunohistochemical stain. Therefore, the tumor was diagnosed as adenomatoid tumor of the testis. Adenomatoid tumors of testis are rare benign neoplasms that are thought to originate from mesothelum. Most cases were reported in the epididymis, spermatic cord and testicular tunica, and rare cases were from the ejaculatory duct, prostate and adrenal gland. The findings of adenomatoid tumor infiltrating through the testis parenchyme and seminiferous tubule, like for our case, have not been previously reported in Korea.