BACKGROUND: Complex, oncologic surgery is an important component of resident education. Our objective was to evaluate the impact of resident participation in oncologic procedures on overall 30-day morbidity and mortality. METHODS: A retrospective cohort analysis was performed using the National Surgical Quality Improvement Program Participant User Files for 2005-2009. Colorectal, hepatopancreaticobiliary, and gastroesophageal oncology procedures were included. Multivariate logistic regression was used to assess the impact of trainee involvement on 30-day morbidity and mortality after adjusting for potential confounders. RESULTS: A total of 77,862 patients were included for analysis, 53,885 (69.2%) involving surgical trainees and 23,977 (30.8%) without trainees. The overall 30-day morbidity was significantly higher in the trainee group [27.2 vs. 21%, adjusted odds ratio (AOR) 1.19, 95% confidence interval (CI) 1.15-1.24, p < 0.0001)]; however, there was significantly lower 30-day postoperative mortality in the trainee group (1.9 vs. 2.1%, AOR 0.87, 95% CI 0.77-0.98, p = 0.02) and significantly lower failure-to-rescue rate (defined as mortality rate among patients suffering one or more postoperative complications) (5.9 vs. 7.6%, AOR 0.79, 95% CI 0.68-0.90, p = 0.001). The overall 30-day morbidity was highest in the PGY 5 level (29%) compared to 24% for PGY 1 or 2 and 23% for PGY 3 (AOR per level increase 1.05, 95% CI 1.03-1.07, p < 0.0001). CONCLUSIONS: Trainee participation in complex, oncologic surgery is associated with significantly higher rates of 30-day postoperative complications in NSQIP-participating hospitals; however, this effect is countered by overall lower 30-day mortality and improved rescue rate in preventing death among patients suffering complications.