A 26-year-old woman had an ovarian Sertoli-Leydig cell tumor (SLCT) associated with an elevated level of serum alpha-fetoprotein (AFP). The tumor had a heterologous element of intestinal-type mucinous epithelium, retiform and intermediately differentiated tubules of the Sertoli cells, and AFP-producing Leydig cells. AFP was demonstrated within the Leydig cells by an immunohistochemical technique. After surgery, the serum AFP level of the patient fell to the normal range. The present case is the first documented case of AFP producing a SLCT of the ovary reported in Korea.