This chapter discusses internationally adopted (IA) children’s post-adoption social development. Findings on child–parent attachment, relationship quality, peer relations, ethnic identity development, self-esteem, and social and academic competence are synthesized in the chapter. The general conclusion from existing research is that IA children perform less well socially and academically than non-adoptees. In addition, differences within IA children and differences between IA children and non-adopted counterparts in all social developmental areas have been widely documented. Typically, when between-group differences exist, they favor adoptees from Asian countries such as China and South Korea. While IA children fare reasonably well social-academically, they have more issues than non-adoptees. Risk factors associated with pre-adoption adversity (e.g., pre-adoption adverse social and emotional experiences) increase vulnerability to develop less optimal social developmental outcomes. This chapter emphasizes that, like the normative non-adoptive population, there are individual and group differences in social and academic outcomes in IA children. Policy implications are discussed in association with promoting post-adoption development.