Background/Purpose: Reoperation is being increasingly utilized as a metric for surgical care quality. The aim of this study was to identify the incidence of and risk factors for unplanned reoperation following index hepatectomy. Methods: Pre, intra- and post-operative information of patients who underwent partial hepatectomy in 435 hospitals participating in the American College of Surgeons National Surgical Quality Improvement Program from 2011 to 2013 were analyzed. Results: 343 (4%) of 9195 patients required reoperation within 30 days of index hepatectomy. The index procedures with the highest incidence of reoperation (%) were trisectionectomy (7%) and right hepatectomy (5%). Patients who underwent reoperation had increased index operative duration (323 ± 174 min versus 243 ± 125 min, p < 0.001), postoperative transfusion (57% versus 23%, p < 0.001), wound complications, cardiorespiratory, renal, thromboembolic, and infectious events. Hemorrhage was the most common indication for reoperation (10%). Male gender, ASA class 4, and right hepatectomy or trisectionectomy were independent predictors of reoperation (OR 1.4 [1.1–1.7], p = 0.007; 2.0 [1.3–3.1], p = 0.003; 1.6 [1.2–2.0], p = 0.001 and 2.5 [1.8–3.4], p < 0.001, respectively). All reoperations occurred during index hospitalization and resulted in longer mean length of stay (19 ± 17 days versus 7 ± 7 days, p < 0.001). Conclusion: Reoperation is associated with several patient characteristics and procedural factors in this national sample. Knowledge of these factors can increase awareness of patients at risk for reoperation. © 2018 International Hepato-Pancreato-Biliary Association Inc.