OBJECTIVE: Although rehabilitation psychology is more focused on empirical evidence and clinical application than theory development, we argue for the primacy of theory, and explain why theories are needed in and useful for rehabilitation psychology. Impediments to theory development are discussed, including the difficulties of applying psychological theories in multidisciplinary enterprises, and the difficulties in developing a theory-driven research program. We offer suggestions by reviewing research settings, knowledge gained through controlled studies, grantsmanship, and then identify topical areas where new theories are needed. We remind researcher-practitioners that rehabilitation psychology benefits from a judicious mix of scientific rigor and real-world vigor. CONCLUSIONS: We close by advocating for theory-driven research programs that embrace a methodological pluralism, which will in turn advance new theory, produce meaningful research programs that inform practice, and realize the goals of this special issue of Rehabilitation Psychology-advances in research and methodology.