Young men who have sex with men (YMSM) continue to be at elevated risk for substance use; however, models explaining this phenomenon have often focused on a limited array of explanatory constructs. This study utilizes Social Action Theory (SAT) as a framework to address gaps in research by documenting the social, behavioral, and demographic risk factors associated with illicit drug use among YMSM. Structural equation modeling was used to apply SAT to a cross-sectional sample of 526 men from the Healthy Young Men Study, a longitudinal study of substance use and sexual risk behavior among YMSM in Los Angeles. The final model possessed very good fit statistics (Comparative Fit Index (CFI) = 0.936, Tucker-Lewis Index (TLI) = 0.925, Root Mean Square Error of Approximation (RMSEA) = 0.040) indicating that SAT is appropriate for use with YMSM. Substance use interventions for YMSM could be enhanced by employing SAT as conceptualized in this study and using a multitargeted strategy for impacting illicit drug use.