<b><i>Objectives:</i></b> We aimed to investigate the nature of endometrial stromal sarcoma (ESS) arising from endometriosis. <b><i>Methods:</i></b> The clinical data of 5 patients with ESS arising from endometriosis were reviewed retrospectively. The expression of CD117, HER2/neu, EGFR, VEGF, and PDGFR was analyzed by immunohistochemical staining. <b><i>Results:</i></b> The median age of the 5 patients was 45 years. The primary tumor sites were the ovary in 2, the pelvis in 2, and the cervical canal in 1 patient. Three patients had disseminated disease at diagnosis. Four patients underwent complete tumor resection. All of the 5 cases received adjuvant chemotherapy and 2 received progesterone therapy, while none were treated with radiotherapy. No recurrence occurred in the 4 cases who had complete tumor resection, and the only patient who progressed was the patient in whom the tumor was unresectable. Tumor cells in all cases exhibited positive staining for PDGFR and were negative for CD117 and HER2/neu. The expression of EGFR and VEGF was observed in 2 and 4 cases, respectively. <b><i>Conclusion:</i></b> ESS arising from endometriosis is rare. Complete tumor resection in ESS arising from endometriosis may reduce the recurrence rate.