Research Findings: The goal of the present study was to examine the moderating role of child effortful control (EC) in the relation between shyness and social-emotional adjustment difficulties among young Chinese children. Participants included 195 children (117 boys, 78 girls, Mage = 4.28 years, SD = 0.31) enrolled in 6 classes attending kindergartens, Shanghai, People's Republic of China. Mothers provided ratings of their children's temperament (shyness, EC) at Time 1, teachers and mothers rated children's social-emotional adjustment at Time 2 (one and a half years later). Results from SPSS PROCESS MACRO revealed several significant interaction effects between shyness and EC in the prediction of outcome variables. Follow-up simple slope analyses indicated that among children with higher levels of EC, shyness was negatively related to mother-reported social-emotional adjustment difficulties, while among children with lower levels of EC, shyness was not associated with mother-reported social-emotional adjustment difficulties. However, among children with lower levels of EC, shyness was positively associated with teacher reported social-emotional adjustment difficulties. In contrast, among children with higher levels of EC, shyness was not associated with teacher-reported social-emotional adjustment difficulties. Practice or Policy: The findings provide evidence to suggest that the combination of shyness and EC may contribute to children's social adjustment, which in turn may promote or attenuate socio-emotional adjustment difficulties.