Temperamental shyness in childhood is theorized to be an important contributor for adolescent personality. However, empirical evidence for such pathways is scarce. Using longitudinal data (N = 939 children, 51% boys) across 17 years, the aim of this study was to examine how shyness development throughout childhood predicted personality traits in adolescence, and the role of peers in these associations. Results from piecewise latent growth curve modeling showed early shyness levels to predict lower emotional stability and openness in adolescence, whereas early shyness levels and growth across childhood predicted lower extraversion. Peer problems in early adolescence accounted for these associations. This study is the first to demonstrate the role of childhood shyness and peer relations for adolescents’ personality development.