Androgen insensitivity syndrome is a disorder of sexual differentiation with 46XY karyotype. The gonad is at risk (33% by 50 years of age) for development of malignant tumors. Hence, gonadectomy is warranted. We present a case of a 22-year-old woman diagnosed with androgen insensitivity syndrome during investigation of primary amenorrhea. Ultrasonography showed intraabdominally-located gonads, with a large, nontender cyst of 9.2 x 5.6 x 5.4 cm size, with limited mobility, to the right of the midline. There was also a partial septum, with a wall thickness of 1 to 2 mm and containing clear fluid. Because of suspicion of malignancy, complete surgery including laparoscopic peritoneal cytologic study, gonadectomy, lymphadenectomy, and omentectomy were performed. Histopathologic study showed testis with an epididymal cyst. Formation of epididymal cyst is rare in these cases. The patient did well in the postoperative period. She was put on hormone replacement therapy and is doing well.