Developmental theory and research have often focused on a single social identity category, for example, race or sexual orientation, and examined the consequences of that category on life outcomes. Yet intersectional models of social disadvantage (eg, Cole, 2009; Crenshaw, 1995; King, 1988) suggest that social categories combine to shape the experiences and life outcomes of individuals across life domains. In this chapter, we review empirical research that offers insight into the intersectionality of social identities across three critical developmental periods, namely, middle childhood, adolescence, and emerging adulthood. We also consider the consequences of intersecting identities across several life domains, including intergroup relations and political and civic engagement. Recognizing that the body of work on social identities is expansive, we focus our review on race/ethnicity, gender, sexual orientation, and immigrant status. In each developmental stage, we discuss what we know, drawing from the limited empirical literature, and offer suggestions on where we need to go moving forward. We conclude that research that focuses on as a single category and ignores the specific domain of development provides an incomplete and inaccurate picture that will hinder efforts to develop culturally appropriate and clinically effective prevention and intervention programs to meet the needs of our diverse children and youth living in the United States.