Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved. Objective: The aim of the study was to evaluate the efficiency and safety of overlapping surgery (OS) at a training institution by comparing it with nonoverlapping surgery (NO) with respect to operative time, mortality, readmissions, and complications. Background: OS is the practice of an attending physician providing supervision to 2 surgeries that are scheduled at overlapping times. Recent media and government attention have raised concerns about this practice and the need for informed patient consent. Methods: A population-based, retrospective, cohort study was conducted using data on operative procedures from January 1, 2014 to December 31, 2015 at a large tertiary academic center. Patients who had undergone surgery by attending surgeons who performed ≥10% of their cases overlapping were selected. Thirty-day mortality, readmission within 30 days, and 7 patient safety indicators (PSIs) were recorded. Results: A total of 26,260 cases met our criteria for analysis for surgical time and 15,106 cases for outcomes. OS patients had an average case length of 2.18 hours compared with 1.64 hours among NO patients (P < 0.0001), a decreased risk of mortality [relative risk (RR) 0.42, 95% confidence interval (CI), 0.34-0.52, P < 0.0001), a decreased risk of readmission (RR 0.92, 95% CI, 0.86-0.98, P = 0.0148), and a decreased risk of experiencing any PSI (RR 0.67, 95% CI, 0.55-0.83, P = 0.0002). Conclusions: The present study confirms prior reports and addresses gaps in the literature regarding OS, such as the effect of resident involvement and the individual effect of OS in 13 different surgical specialties. The findings highlight the need for additional investigation and suggest that the practice of OS does not expose patients to increased risk of negative outcomes.