AbstractObjectiveTo determine whether deep‐infiltrating endometriosis (DE) carries an increased risk of appendiceal endometriosis (AppE) as compared with superficial endometriosis or no endometriosis.MethodsIn a retrospective study, data were obtained by chart review of an internal database for women who underwent coincidental appendectomy during benign gynecologic surgery between July 2009 and February 2014 at a tertiary referral center in the USA. Univariate, bivariate, and regression analyses were performed. The primary exposure was surgically documented endometriosis (DE, superficial, or no endometriosis). The primary outcome was AppE.ResultsEndometriosis was diagnosed for 151 (38.2%) of 395 women; 82 (54.3%) had DE. The prevalence of AppE was 13.2% (52/395) overall; 8 (11.6%) of 69 women with superficial endometriosis and 32 (39.0%) of 82 with DE were affected. Frequency of AppE was increased among women with DE, abnormal appendix appearance, and surgical indication (all P<0.001). Women with DE had a 5.9‐fold (95% confidence interval [CI] 2.9–11.9) higher risk of AppE compared with women without endometriosis, controlling for appendiceal appearance and surgical indication, and a 2.7‐fold (95% CI 1.2–6.2) higher risk of AppE compared with those with superficial endometriosis.ConclusionWomen with DE have increased risk of AppE. Coincidental appendectomy should form part of complete endometriosis excision for these patients.