Neonatal testicular tumors and intrauterine testicular torsions are very rare. The presented case is the first describing intrauterine torsion of a descended testis with a teratomatous tumor. Immediately after birth, right hemiscrotal swelling was seen in a preterm male newborn. Surgical intervention showed extravaginal testicular torsion and a highly differentiated testicular teratoma with haemorrhagic infarction. The testis was removed (orchiectomy). Over a period of twelve months no signs of tumor recurrence were found. While being extremely rare, testicular tumors should be included in the differential diagnosis of neonatal scrotal swelling.