Character-based video games do more than allow one to practice various kinds of behaviors in a virtual environment; they allow one to practice being a different kind of person. As such, we propose that games can alter self-perceptions of personal characteristics, attitudes, and values with broad consequences for behavior. In a multiwave, longitudinal study of adolescents, we examined the extent to which play of mature-rated, risk-glorifying (MRRG) games was associated with increases in alcohol use, cigarette smoking, aggression, delinquency, and risky sex as a consequence of its effects on personality, attitudes, and affiliations indicative of increased tolerance of deviance. Participants were selected with random-digit-dial procedures and followed for 4 years. Data were analyzed with linear mixed modeling to assess change over time and structural equation modeling with latent variables to test hypothesized mediational processes. Among those who play video games, playing MRRG games was associated with increases in all measures of behavioral deviance. Mediational models support the hypothesis that these effects are in part a consequence of the effects of such gameplay on sensation seeking and rebelliousness, attitudes toward deviant behavior in oneself and others, and affiliation with deviant peers. Effects were similar for males and females and were strongest for those who reported heavy play of mature-rated games and games that involved protagonists who represent nonnormative and antisocial values. In sum, the current research supports the perspective that MRRG gameplay can have consequences for deviant behavior broadly defined by affecting the personality, attitudes, and values of the player.