Objective To evaluate the ovarian reserve changes after laparoscopic cystectomy, we prospectively evaluated pre- and postoperative serum anti-Müllerian hormone (AMH) level, and ovarian volumes. Design Prospective longitudinal study. Setting University Hospital. Patient(s) Twenty women with benign ovarian masses participated; endometrioma 13, mature teratoma 6, and mucinous cystadenoma 1. Seven patients had bilateral ovarian masses. Intervention(s) All patients had undergone laparoscopic ovarian cystectomy. Serum AMH levels were serially measured: preoperative, 1 week, 1 month, and 3 months after operation. Volumes of total ovary and ovarian mass were measured by 3D ultrasonography before operation. Main Outcome Measure(s) Postoperative serum AMH level and ovarian volume. Result(s) Median AMH level was 2.23 ng/mL (95% confidence interval CI 1.35–3.41 ng/mL) before operation, but reduced to 0.67 ng/mL (95% CI 0.44–1.70 ng/mL) at the first week postoperatively and then increased to 1.14 ng/mL (95% CI 0.79–2.36 ng/mL) in the first month and 1.50 ng/mL (95% CI 0.58–3.26 ng/mL) in the third month. The serum AMH level after 3 months postoperatively was recovered to about 65% of the preoperative level. The serum AMH level at postoperative 1 week was more decreased in endometrioma compared with nonendometrioma (33.9% vs. 69.2% of preoperative level), and in bilateral group compared with unilateral group (16.9% vs. 62.9%). Conclusion(s) This study suggests that ovarian reserve could be reduced after laparoscopic cystectomy; however, it could be restored thereafter up to 3 months postoperative in reproductive women.