A 19-year-old girl of 45,X/46,XY mosaic Turner syndrome, presenting with short stature, sexture, sexual infantilism and abnormal physical stigmata was found to have a left adnexa mass at diagnosis. The mass was proved to be gonadoblastoma and dysgerminoma after surgical intervention. The risk of developing gonadal tumor from the streak gonad in patients of Turner syndrome with Y chromosome mosaicism should be emphasized.