A case of a 58-year-old woman with ovarian carcinoid exhibiting double function is reported. She had suffered from constipation and hirsutism before surgery. Pathological examination revealed that many carcinoid tumor cells were immunohistochemically positive for peptide YY, which inhibits intestinal motility and many peripheral steroid cells. After surgery the patient recovered from constipation immediately. Although the serum level of testosterone also immediately decreased, hirsutism remained for about 2 years. These clinical manifestations are considered to be due to peptide hormone-producing tumor parenchymal cells and testosterone-producing functioning stromal cells. This is the first report of clinically manifested double-functioning ovarian carcinoid; one function is due to tumor cells themselves and another function is due to stromal cells.