Breast reduction surgery is a common and effective surgical technique for treating symptomatic macromastia. There is limited data on the impact of resident involvement on outcomes. This study uses the ACS-NSQIP datasets to assess the impact of surgical resident participation in breast reduction surgery. This study reviewed the 2005-2011 ACS-NSQIP databases identifying primary encounters for reduction mammaplasty with CPT code "19318". It characterised surgical complications into three groups: any, major, and wound complications. Propensity scoring and matched analysis were used to account for non-randomised assignment. In total, 4328 patients underwent reduction mammoplasty during the study period. Resident participation was identified in 56.3% of cases. Logistic regression analysis determined the following factors independently associated with resident participation: class II obesity (OR = 0.73, p < 0.001), class III obesity (OR = 0.68, p < 0.001), dyspnea (OR = 1.59, p = 0.04), and ASA physical status of 3 (OR = 1.51, p < 0.001). A propensity score was assigned based on probability of resident involvement and matched cohorts were created and analyzed. A logistic regression analysis of the matched cohort data revealed that resident participation was independently associated with major surgical complications (OR = 2.18, p = 0.008). Prolonged operative (>2 SD) was associated with any (OR = 3.3, p = 0.039) and wound (OR = 10.2, p = 0.028) complications. A separate logistic regression analysis of the unmatched cohort using stratified PGY experience demonstrated that junior PGY was most highly associated with any (OR = 1.93, p = 0.013), major (OR = 2.4, p = 0.034), and wound (OR = 1.9, p = 0.04) complications. Resident participation was associated with added risk of surgical morbidity, and PGY experience was inversely related to risk of surgical complications in breast reduction surgery.