There is a paucity of data regarding patients undergoing emergency surgery following radiotherapy. This study examines the morbidity and mortality of patients having emergent surgery a parts per thousand currency sign90 days after irradiation. We identified patients a parts per thousand yen18 years of age in the American College of Surgeons National Surgical Quality Improvement Program (Radiation group) who underwent irradiation a parts per thousand currency sign90 days before emergency surgery. Patients receiving concomitant chemotherapy were excluded. Subjects were compared to a Control group that did not have preoperative irradiation but underwent similar emergent procedures (matched 1:1 on age and procedure). Demographic and clinical characteristics, including patient co-morbidities, functional status, and preoperative laboratory values, were assessed. Primary outcomes included 30-day postoperative morbidity and mortality. Log-transformed data, bivariate and multivariate linear and conditional logistic regression were used. A total of 536 patients were included, 268 per group. Patient demographics and preoperative co-morbidities were similar between groups. The Radiation group had more mortality [23.9% vs. 11.6%, P < 0.001; odds ratio (OR) 2.4], major complications (45.1% vs. 34.7%, P = 0.014; OR 1.55), and a greater likelihood of sustaining a complication (48.1% vs. 38.1%, P = 0.019; OR 1.51). Days from admission to operation, operating time, likelihood of reoperation, days from operation to death, and length of hospital stay were not statistically different. By conditional logistic regression, death was independently associated with irradiation, chronic obstructive pulmonary disease (COPD), impaired preoperative functional status, and thrombocytopenia; and a major complication was associated with COPD, hypoalbuminemia, and preoperative wound infection. Patients who require emergent surgery a parts per thousand currency sign90 days after irradiation sustain increased morbidity and mortality. Optimizing the nutritional and functional status of these patients may improve surgical outcomes.