Scholars have called for theoretical and empirical efforts to understand the linkages between identity theory (IT) and social identity theory (SIT). IT has focused on “role” identities, while SIT focuses on “social” identities. These theories have developed in isolation, although scholarly discussions of each identity’s theoretical and substantive import have occurred. Some assert that synthesizing IT and SIT will provide a more general theory of the self, offering a parsimonious account of processes (e.g., micro-macro links, interpersonal-intergroup) that are traditionally addressed under one theory. Consistent with these calls, we attempt a theoretical and empirical comparison of the two theories. Our focus is on four main points of comparison: (1) meta-theoretical assumptions, (2) principles determining salience, (3) the cognitive processes underpinning each type of identity, and (4) their respective self-concept functions. We use data from The Science Study, which contains a longitudinal sample of minority students seeking careers in STEM fields, to test hypotheses derived from a synthesis of insights across IT and SIT. Results suggest that similar principles govern role and social identities.