Over the last 25 years, there has been a noteworthy turn across major International Relations (IR) theories to include domestic politics and decision-making factors. Neoclassical realism and variants of liberalism and constructivism, for example, have incorporated state motives, perceptions, domestic political institutions, public opinion, and political culture. These theoretical developments, however, have largely ignored decades of research in foreign policy analysis (FPA) examining how domestic political and decision-making factors affect actors’ choices and policies. This continues the historical disconnect between FPA and “mainstream” IR, resulting in contemporary IR theories that are considerably underdeveloped. This article revisits the reasons for this separation and demonstrates the gaps between IR theory and FPA research. I argue that a distinct FPA perspective, one that is psychologically oriented and agent-based, can serve as a complement, a competitor, and an integrating crucible for the cross-theoretical turn toward domestic politics and decision making in IR theory.