Background: The Centers for Disease Control and Prevention estimates that nearly 40% of the U.S. population meets the criteria for obesity classification. Several studies have shown that obesity is associated with increased medical morbidity and costs. In this study, we investigated the impact of obesity on the financial burden of radical cystectomy. We hypothesize that the cost of radical cystectomy is greater in obese and morbidly obese patients compared to overweight patients. Methods: We performed a retrospective observational study within the Premier Healthcare Database (Premier Inc., Charlotte, NC), a large, U.S. hospital-based, all-payer database representing approximately 20% of annual inpatient discharges. ICD-9 procedure codes were used to identify all patients who had undergone elective radical cystectomy (57.71, 57.79) from 2003 to 2015, and administrative data was used to extract the costs associated with the index hospitalization. Patients were stratified into three body mass index (BMI) categories: overweight (25 BMI <30), obese (30 ≤ BMI < 40) and morbidly obese (BMI ≥ 40). Quantile regression analysis was performed to examine the effect of BMI category on cost. Results: We identified 12,056 patients who underwent radical cystectomy, 1,406 of whom had data available regarding BMI category. The crude cost of the index hospitalization for radical cystectomy was $24,596 for overweight patients. The costs associated with patients in the obese and morbidly obese categories were $2,158 (p=0.059) and $5,308 (p<0.001) higher compared to overweight patients, respectively. Median operative time for overweight, obese, and morbidly obese patients was 346, 391, and 420 minutes, respectively (p=0.0001). Multivariable models were constructed controlling for clinicodemographic, and surgical factors. After adjustment for operative time, there were no longer any statistically significant differences in cost between the BMI categories. Conclusions: The cost of radical cystectomy is significantly greater for obese and morbidly obese patients compared to overweight patients. This increased financial cost associated with obesity difference is driven by increased operative times encountered in obese patients.