OBJECTIVE: To identify whether resident involvement affects clinically relevant outcomes in emergency general surgery. BACKGROUND: Previous research has demonstrated a significant impact of trainee participation on outcomes in a broad surgical patient population. METHODS: We identified 141,010 patients who underwent emergency general surgery procedures in the 2005-2010 Surgeons National Surgical Quality Improvement Program database. Because of the nonrandom assignment of complex cases to resident participation, patients were matched (1:1) on known risk factors [age, sex, inpatient status, preexisting comorbidities (obesity, diabetes, smoking, alcohol, steroid use, coronary artery disease, chronic renal failure, pulmonary disease)] and preoperatively calculated probability for morbidity and mortality. Clinically relevant outcomes were compared with a t or χ test. The impact of resident participation on outcomes was assessed with multivariable regression modeling, adjusting for risk factors and operative time. RESULTS: The most common procedures in the matched cohort (n = 83,790) were appendectomy (39.9%), exploratory laparotomy (8.8%), and adhesiolysis (6.6%). Trainee participation is independently associated with intra- and postoperative events, wound, pulmonary, and venous thromboembolic complications, and urinary tract infections. CONCLUSIONS: Trainee participation is associated with adverse outcomes in emergency general surgery procedures.