Drawing upon a sample of 772 migrant children and their parents in Shanghai, China, this study used an ecological framework to investigate how social capital embedded in a range of social contexts (i.e., family, school, peer, and community) influenced the psychosocial adjustment of Chinese migrant children. Using structural equation modeling with latent variables, the study results suggested that higher levels of family, school, and peer social capital were all associated with better psychosocial adjustment of migrant children, with school social capital showing the strongest effect. In addition, these three dimensions of social capital also mediated the effect of community social capital on children’s psychosocial adjustment. Implications of these findings for theory, practice, and future research were discussed.