Purpose: Research shows that parenting factors and individual difference variables, such as sensation seeking (SS) and risk perceptions (RPs), are associated with increased motor vehicle crash risk for young drivers. The presence of peer passengers is also known to be associated with increased crash risk. However, as previous studies did not study these factors concurrently, less is known about the factors that are associated with driving with peer passengers and if peer passengers may mediate the effect of parenting and individual difference variables on adolescents' engagement in risky driving behavior. Methods: We examined predictors of driving with multiple passengers (DWMPs) and explored it as a potential mediator of pathways from three factors: (1) SS, (2) RPs, and (3) Parental monitoring and rule-setting to risky driving behaviors in a convenience sample of 198 adolescent drivers using a cross-sectional Web-based survey. Results: Findings indicate that both stronger RPs and perceiving parents as strong monitors and rule setters were associated with less engagement in risky driving, whereas greater SS was associated with more engagement in risky driving; RPs, monitoring, and SS were also significantly associated with DWMPs in these same directions. DWMPs partially mediated the effect of these risk factors on risky driving behavior. Conclusions: Results inform theory and policy by examining factors associated with risk taking in the context of adolescent driving. Interventions can be developed to complement graduated driver licensing laws by targeting individual difference variables and decreasing opportunities for peer passenger carriage. © 2012 Society for Adolescent Health and Medicine.