The strong correlation between measures of personal and peer deviance occurs with near “law‐like” regularity. Yet, as with other manifestations of peer similarity (often referred to as homophily), the mechanisms generating this relationship are widely debated. Specific to the deviance literature, most studies have failed to examine, simultaneously, the degree to which similarity is the consequence of multiple causes. The current study addresses this gap by using longitudinal network data for 1,151 individuals from the Netherlands Institute for the Study of Crime and Law Enforcement (NSCR) School Project. Structural equation modeling is used to address these issues by adapting Jussim and Osgood's () model of deviant attitudes in dyadic pairs to the current data. Across two separate behavioral domains (substance use and property offending), the results provide strong support for the prediction that individuals project their own deviant tendencies inaccurately onto their peers. Conversely, the results provide little or no support for the predictions that respondents accurately perceive their peers’ deviance or that their perceptions of peer deviance influence their own behavior. Implications for understanding the role of peer behavior in the etiology of adolescent deviance are discussed.