Objective To compare the impact of obesity on perioperative outcomes between open radical prostatectomy (ORP) and minimally invasive prostatectomy (MIP). Methods Using the National Surgical Quality Improvement Program public use files for 2008-2013, we identified patients undergoing prostatectomy using Current Procedural Terminology codes. Those without body mass index (BMI) or comorbidity information were excluded. BMI was treated as a categorical variable according to the World Health Organization classification. Demographic and comorbid conditions were compared between BMI groups, and multivariable logistical regression was used to identify independent predictors of adverse perioperative events. Results We identified 17,693 MIP and 4674 ORP for analysis. Of the entire cohort, only 18.7% had a BMI within the normal range (18.5-24.9), whereas the remaining 81.3% were at least overweight (BMI > 25). Class I, II, and III obesity accounted for 25.0%, 7.0%, and 2.3% of the cohort, respectively. Overall, complications were higher with ORP (19.0%) than with MIP (5.3%), which held true across all BMI categories. The rate of wound, renal, thromboembolic, infectious, neurologic, Clavien grade III-V, and overall complications among MIP were directly related to BMI. Only wound and renal complications were related to BMI in ORP. In multivariable analysis, obesity was found to be an independent predictor of wound, renal, and thromboembolic complications. Conclusion Obesity has a larger impact on morbidity for MIP compared to ORP. Overall morbidity, however, remains lower for MIP across all BMI groups.