Laparoscopic adnexal surgery emerged as an alternative to laparotomy in the mid-1990s. It is associated with less morbidity and pain, reduced length of hospital stay, and reduced costs compared with laparotomy. For these reasons, laparoscopy has become the standard of care for benign adnexal surgery. Over the last 2 decades, robotically assisted surgery has been used for many procedures, but little is known about robotically assisted adnexal surgery. Outcome data for robotically assisted adnexal surgery are limited and based on single-center experiences. This population-based study compared the complications and cost of laparoscopic and robotically assisted adnexal surgery. A nationwide database was used to analyze outcomes of robotically assisted adnexal surgery from 2009 to 2012. Participants underwent either laparoscopic oophorectomy (with or without salpingectomy) or laparoscopic ovarian cystectomy. Predictors of use of robotic surgery were examined using multivariable mixed-effects regression models. After propensity score matching, complications and cost of robotically assisted and laparoscopic surgery were compared. A total of 87,514 women were identified; of these, 52,999 underwent oophorectomy, and 34,915 underwent cystectomy. During the study period, use of robotic-assisted oophorectomy increased yearly from 3.5% (95% confidence interval [CI], 3.2%–3.8%) to 15.0% (95% CI, 14.4%–15.6%), and robotically assisted cystectomy increased annually from 2.4% (95% CI, 2.0%–2.7%) to 12.9% (95% CI, 12.2%–13.5%) (both comparisons, P < 0.001). The overall complication rate for robotically assisted oophorectomy was 7.1% (95% CI, 4.0%–10.2%) compared with 6.0% (95% CI, 2.9%–9.1%) for laparoscopic oophorectomy; the odds ratio (OR) was 1.20, with a 95% CI of 1.00–1.45, P = 0.052. Robotic-assisted oophorectomy was also associated with a higher rate of intraoperative complications (3.4% vs 2.1%; OR, 1.60; 95% CI, 1.21–2.13; P < 0.001). With respect to cystectomy, the overall complication rate after the robotically assisted procedure was 3.7% (95% CI, −0.8% to 8.2%) and 2.7% (95% CI, −1.8% to 7.2%) for the laparoscopic technique (OR, 1.38; 95% CI, 0.95–1.99). Robotically assisted cystectomy was associated with a higher rate of intraoperative complications compared with laparoscopy (2.0% vs 0.9%; the OR was 2.40, with a 95% CI of 1.31 to 4.38. Robotically assisted oophorectomy was associated with $2504 (95% CI, $2356–$2652) more total costs and robotically assisted cystectomy $3310 (95% CI, $3082–$3581) more total costs than laparoscopy. These findings show that use of robotically assisted adnexal surgery increased rapidly from 2009 to 2012. Robotically assisted adnexal surgery was associated with substantially greater costs and a small, but statistically significant, increase in intraoperative complications compared with laparoscopic surgery.