We report a 36-year-old patient who presented with primary amenorrhea and was found to have a giant abdominal tumor. There was a family history of primary amenorrhea in her two aunts. Physical and hormonal examinations as well as chromosomal analysis led to a diagnosis of testicular feminization. The patient underwent tumorectomy along with pelvic and para-aortic lymphadectomy. The pathological diagnosis was bilateral seminoma of the testis with metastasis to para-aortic lymph nodes. Nowadays, cases of undiagnosed seminoma developing into a huge abdominal mass in patients with testicular feminization are rarely encountered, since surgical castration is generally recommended as early as possible after puberty. In testicular feminization, the risk of malignant transformation of the dysgenetic male gonads increases substantially after puberty. Early and correct diagnosis together with careful follow-up are critically important in managing testicular feminization, a rare congenital disorder.