Over the past decade, developmental and social psychological research has explicitly adopted a developmental intergroup framework, integrating social and developmental psychology fields to understand the origins of social exclusion and prejudice. This article argues that a social developmental analysis of how groups and individuals experience, evaluate, and understand exclusion is essential for a complete picture of the human experience, interpretation, and consequences of exclusion. What has been missing in much of the social psychological research on exclusion is an incorporation of developmental perspectives; likewise, what has been missing in development psychological research is a focus on group identity and group dynamics for understanding the basis for exclusionary behavior in childhood. Yet, the roots of adult forms of exclusion can be documented in childhood, and children who experience exclusion are particularly at risk for negative outcomes, and especially when exclusion is based on group membership. Moreover, interventions designed to ameliorate social problems associated with exclusion need to be based on an understanding of how, why, and under what conditions, children and groups make decisions to exclude others, how they experience this exclusion, and how exclusion originates and changes over the course of the lifespan. Thus, a growing body of psychological work, exemplified in this issue of the Journal of Social Issues (2014), highlights implications for theory in psychology and related social sciences, and for interventions and policies to tackle social exclusion.