The market-oriented economic reform in China over the past two decades has resulted in considerable changes in social attitudes regarding youth's behaviors. This study examined the relations of shyness and aggression to adjustment in Chinese adolescents at different historical times. Participants came from two cohorts (1994 and 2008) of adolescents in Shanghai (N = 540 and 728, respectively; M age = 13 years), and data were obtained from multiple sources. Although aggression was associated with adjustment problems in both cohorts, there were significant cross-cohort differences in the relations between shyness and adjustment. In the 1994 cohort, shyness was positively associated with teacher-rated competence, leadership, and academic achievement. In the 2008 cohort, however, shyness was negatively associated with peer preference and positively associated with loneliness. (Contains 2 tables.)