Background: Ovarian atypical endometriosis(AE) has been recognized as a premalignant lesion and the existence of the endometriosis associated ovarian cancer further emphasizes its importance. The true risk of malignancy in AE remains unclear. The purpose of this study is to investigate the clinical results of ovarian AE after ovarian cystectomy. Materials and Methods: We retrospectively reviewed the medical records and histopathological reports of 41 patients who were diagnosed with ovarian AE between January 2011 and April 2020. We reviewed age, obstetric history, menarche age, preoperative CA 125 level, CRP, ESR, endometriois stage , mean follow up period, postoperative hormonal therapy and prognosis such as recurrence of endometrosis or malignant transformation. Results: Among the 41 patients with ovarian AE pathologically diagnosed, 26 patients were under follow-up after performing only cystectomy, excluding patients with EAOC or other diseases and patients who underwent oophorectomy. Postoperative hormonal therapy was performed on all but 4 out of 26 patients. There was recurrence of endometriosis in five patients, one of whom underwent second-line laparoscopic ovarian cystectomy. However, there was no malignant transformation. Conclusion: Ovarian AE has a very low possibility of malignant transformation. Conservative treatment is recommendable after an appropriate ovarian cystectomy such as enucleation.