Undescended testis is most common congenital malformation in boys. Most common location is inguinal canal but rarely it is found in intraabdominal. 10% of them will grow become mass if left untreated. This case report describes cases of men of 40s with unilateral UDT and not noticeable until they felt heavy and feel palpable mass in abdomen revealed as seminoma. He is sterile and not be able to reproduce. Chemotherapy was done and the response was remarkable. This case report reiterates the need for a scrotal examination in men presenting with an abdominal mass, so as to rule out an intra-abdominal seminoma.