The effect of surgery resident participation on breast cancer recurrence has not been previously reported. The objectives of this study were to determine if resident participation was associated with either immediate postoperative or long-term breast cancer outcomes.We retrospectively reviewed a prospectively collected breast center database to identify all patients with breast cancer undergoing surgery in a single center during a 9-year period ending 1 January 2010. Patients were divided into 2 groups based on whether surgery residents completed more than 50% of the critical portions of the case (Resident group) or not. The outcomes of operation length, reoperative rates, morbidity, and the long-term outcomes of cancer recurrence were compared by group. Comparisons of immediate postoperative outcomes were made with chi-square and Fisher exact tests. Comparisons of operation length were analyzed by Wilcoxon rank-sum testing. Survival analyses were calculated using the Kaplan-Meier method with log-rank comparison. Multivariate analysis with Cox regression was also performed.The study occurred at a community-based hospital that has an accredited general surgery training program.In all, 1107 consecutive patients with stage 0–3 breast cancer undergoing breast cancer operations were included.Median age of patients was 64 years (range: 24-97). Median and longest follow-up were 5.5 and 12.5 years, respectively. Initial operation was breast conserving in 796 (72%) and mastectomy in 311 (28%). Of the 1107 patients, 887 (80.1%) had resident participation. The Resident group was associated with longer operative times. We identified no differences in operative morbidity, reoperations, overall survival, disease-free survival, or local-regional recurrence in the Resident and No Resident groups.Resident involvement in breast cancer operations was associated with longer operative times but did not affect any other perioperative or cancer outcome in our institution. This information can be used to reassure program directors, attending surgeons, and patients if they have questions or concerns about the safety or effectiveness of cancer surgery when there is surgical resident participation.