This study aimed to evaluate the effect of within-endobag cystectomy during and after laparoscopic ovarian cystectomy in patients with dermoid cysts. We retrospectively analyzed 84 patients with ovarian dermoid cysts who underwent laparoscopic ovarian cystectomy. In 30 patients, the affected ovary was placed in an endobag before cystectomy and cystectomy was performed within an endobag (within-endobag group), while the remaining 54 patients underwent standard cystectomy without this step (without-endobag group). After cystectomy, the cyst wall was placed in an endobag and was removed from the abdomen. Compared with the without-endobag group, the within-endobag group had a significantly lower rate of cyst content spillage (23.3% vs 72.2%, P < .001) and significantly shorter operation times when the cysts ruptured (23.4 ± 8.6 minutes vs 51.2 ± 28.6 minutes, P < .001). Whereas there was no significant difference in operation time in the absence of cyst rupture between 2 groups (21.2 ± 8.8 minutes vs 31.1 ± 17.4 minutes, P = .111). In patients with cyst rupture, according to the cyst size increase, the operation time was significantly prolonged without-endobag, whereas no significant prolongation was observed in within-endobag cystectomy. Except for operation time, there were no significant differences in cyst length, pain on the first day after surgery, hemoglobin loss, hospital stay, and inflammatory markers (C-reactive protein and white blood cell counts) in both ruptured and unruptured cases between the 2 groups. There were no postoperative complications in the within-endobag group, but 2 cases of perioperative complications occurred in the without-endobag group. No chemical peritonitis due to spillage of the cyst contents was observed in either group. Laparoscopic ovarian cystectomy performed within-endobag can reduce both the spillage rate of cyst contents and operation time regardless of cyst size in patients with ruptured cysts. Therefore, this technique is a good surgical option for the laparoscopic ovarian cystectomy of large dermoid ovarian cysts.