Patients undergoing radical pelvic surgery such as proctectomy or radical cystectomy are at risk of experiencing a variety of complications. Frailty renders patients vulnerable to adverse events. We hypothesize that frailty measured preoperatively using a validated scoring system correlates with increased likelihood of experiencing Clavien-Dindo grade IV complications and 30-day mortality and may be used as a predictive model for patients preoperatively. The NSQIP database was queried for patients who underwent proctectomy or radical cystectomy from 2008 to 2012. Preoperative frailty was calculated using the 11-point modified frailty index (MFI). Patients were scored based on the presence of indicators and categorized into two groups (<3 or ≥3). Major postoperative morbidities and mortality were identified and analyzed in each group. 10,048 proctectomy and cystectomy patients were identified. The MFI was found to be predictive of both 30-day mortality (P < 0.0001) and Clavien-Dindo grade IV complications (P < 0.0001). Receiver operating characteristic analysis demonstrated improved discriminative power of the MFI with the addition of American Society of Anesthesiologists class for both prediction of complications and 30-day mortality. An MFI score of ≥3 is predictive of postoperative morbidity and mortality. Providers should be encouraged to calculate frailty preoperatively to predict adverse outcomes.