Background: Endometriosis is the presence of endometrial glands or stroma in sites other than the uterine cavity such as the ovaries, fallopian tubes and the pelvis. The most common location of endometriosis is the ovary, occurring in 17-44% of patients affected by endometriosis. Objectives: To explore the impact of laparoscopic ovarian cystectomy versus aspiration and coagulation on ovarian reserve in cases of ovarian endometrioma. Patients and Methods: This randomized controlled prospective study was conducted on ninety two patients presenting with unilateral ovarian endometrioma at Obstetrics and Gynecology Department, Al-Azhar University Hospitals during the period from April 2018 to October 2019. FSH, LH, E2, AMH, AFC (antral follicular count); all were determined before and after laparoscopic surgery (postoperative three months); for two groups: Group A for cystectomy and Group B for aspiration and coagulation, performed randomly using closed envelope. Histopathological examination was done to the cystectomy group to confirm endometriosis and detect the presence of healthy ovarian tissue in the excised cyst wall. Results: There were postoperative significant decreases in FSH, LH, E2, AMH and AFC in each group compared with the preoperative values but were within normal ranges, and this decrease was of no statistically significant difference between both groups as regarding (FSH, LH, E2, AMH). There was a statistically significant difference between both groups in AFC which was more decreased in the cystectomy group. So, AFC was more accurate in predicting ovarian reserve loss than AMH. Conclusion: Ovarian reserve decreased by both techniques; but the decrease was more frequent in cystectomized ovaries.