We investigated deviant peer associations as a mediator of the influences of general and peer-oriented self-esteem on problem behavior using data from a 2-year longitudinal study of 350 young adolescents. Measures of problem behavior included substance use (alcohol use, smoking) and antisocial behavior (fighting, stealing). Using latent growth curve modeling and covariance structure analysis, an extension of a model proposed by DuBois et al. (2002) was evaluated for each type of problem behavior. Findings revealed that lower general self-esteem and greater peer orientation in self-esteem each predicted deviant associations with peers and that deviant peer associations, in turn, were associated with higher levels and rates of change in problem behavior. Deviant peer associations mediated the associations of general and peer-oriented self-esteem with levels and rates of change in problem behavior such that direct paths from self-esteem to problem behavior generally were nonsignificant.