Intersectionality theory concerns the interdependence of systems of inequality and implications for psychological research. Social identities cannot be studied independently of one another nor separately from the societal processes that maintain inequality. In this chapter we provide a brief overview of the history of intersectionality theory and then address how intersectionality theory challenges the way psychological theories typically conceive of the person, as well as the methods of data gathering and analysis customarily used by many psychologists. We specifically address two concerns often expressed by feminist researchers. First, how to reconcile the use of an intersectionality framework with currently-valued psychological science practices. Second, how intersectionality transforms psychology’s concern with individual experience by shifting the focus to the individual’s position within sociostructural frameworks and their social and political underpinnings. In a concluding section we identify two future directions for intersectionality theory: how psychological research on intersectionality can facilitate social activism, and current developments in intersectionality theory.