The effects of peers on three domains of alcohol expectancies through early adolescence were prospectively examined over two years. Information on pubertal development, parental drinking, peer characteristics, network structure, alcohol expectancies, and alcohol consumption was assessed in a three-wave longitudinal study of 779 6th graders (~ 12 years of age) randomly selected from northern Taiwan. Complex survey regression analyses, stratified by drinking experience in 6th grade, were performed to identify predictors of two positive (i.e., enhanced social behaviors and relaxation/tension reduction) and one negative alcohol expectancies (i.e., cognitive/behavioral deterioration) in 7th grade. The results showed that the effects of peer influence on adolescents’ alcohol expectancies varied by prior drinking experiences and by expectancy domains. For the alcohol naïve, recent exposure to peer drinking was significantly associated with positive and negative alcohol expectancies in grade 7, and this association was moderated by advanced pubertal development (ESBlate puberty: ßwt = 0.55; ESBearly puberty: ßwt = -0.40; PRTRlate puberty: ßwt = 0.01; PRTRearly puberty: ßwt = 1.22; CBD late puberty: ßwt = -0.84; CBDearly puberty: ßwt = 0.56). For the alcohol experienced, neither peer drinking nor pubertal development showed any significant links with alcohol expectancies. Occupying a bridge position was slightly linked with negative expectancy (ßwt = 0.25). Concurrent drinking serves as a strong predictor for the endorsed alcohol expectancy in both groups, particularly for the domain of enhanced social behaviors. If these effects are confirmed, knowledge of the effect of interplay between peer factors and pubertal development on alcohol expectancies in early adolescence can provide effective targets in prevention programs.