Muscle building behaviors are an understudied eating disorder (ED) symptom increasing in prevalence, especially among men. However, little is known about the cognitive ED correlates that may underlie muscle building behaviors and whether these associations differ by gender. We examined associations between cognitive ED symptoms and muscle building behaviors, and whether these associations differ between men and women. In a sample of college students (N = 258), we investigated cross-sectional associations between two core cognitive ED symptoms, body dissatisfaction and cognitive restraint, with muscle building behaviors, and whether binary gender moderated these associations. Data were analyzed using two linear regression models in which muscle building behaviors was entered as the outcome variable. In Model 1, body dissatisfaction, BMI, gender, and the interaction term of body dissatisfaction by gender were entered as predictors. In Model 2, cognitive restraint, BMI, gender, and the interaction term of cognitive restraint by gender were entered as predictors. Results of Model 1 indicated that muscle building behaviors were significantly and independently associated with body dissatisfaction and gender and the association between muscle building and body dissatisfaction was stronger for men. Results of Model 2 indicated that muscle building behaviors were significantly and independently associated with cognitive restraint and gender and the association between muscle building and cognitive restraint was stronger for men. Findings suggest that cognitive restraint and body dissatisfaction may be important prevention and intervention targets for maladaptive muscle building behaviors, particularly among men.