The present study examined the mechanisms by which family environment, parent--grandparent coparenting, effortful control, and early child-care experiences influenced young children's social adaptation in the Chinese context. A sample of 315 mothers of 2-3-year-olds (M = 33.36 months; SD = 5.10) in Beijing, China completed questionnaires to report children's temperament, family process, and children's social adaptation. Using the approach of conditional process analysis, the results revealed moderated mediation models that children's effortful control had a mediating effect on the association between their family process and social adaptation, while the effect of effortful control on social adaptation was contingent on children's early child-care experiences, with a stronger positive effect of effortful control among children who engaged for longer periods of child-care experiences. Findings point to the importance of understanding the role of family process and children's effortful control in the early development of social adaptation.