Research examining the relationship between body mass index (BMI) and sexual risk outcomes among men who have sex with men (MSM) has yielded inconsistent results. Using a web-based survey, single-identified (e.g., not in a relationship) young MSM (N = 431) between the ages of 18 and 24 years who sought romantic partners online were asked to respond to items regarding their BMI, body image (e.g., attribution, dissatisfaction, and pride), and sexual risk behaviors. We used Poisson regressions to examine the relationships between BMI, body image, and the number of unprotected receptive anal intercourse (URAI) occasions and partners in the past 2 months. We found a curvilinear relationship between BMI and URAI occasions, and a linear relationship between BMI and URAI partners. These relationships persisted after accounting for body image. Further, we found that body attribution served as a protective factor whereas body pride served as a risk factor. We discuss the implications of our findings for sexual health education and HIV prevention.