Much of the literature on interprofessional education (IPE) is descriptive, anecdotal, and atheoretical. To advance both practice and research in this field, IPE needs to develop theoretical frameworks that: (i) identify major concepts to guide the development of course and program structures and processes, (ii) specify learning objectives and effective methods for their achievement, (iii) suggest appropriate roles for faculty and students in the educational process, and (iv) aid in research and assessment of program impacts and outcomes. Following an exploration of what theory should mean and the role it might play in advancing IPE, this discussion surveys five different theoretical approaches for guidance in developing an IPE framework: (i) cooperative, collaborative, or social learning; (ii) experiential learning; (iii) epistemology and ontology of interdisciplinary inquiry; (iv) cognitive and ethical student development; and (v) education of the reflective practitioner. Common themes are discussed and their implications for IPE are explored. These include: (i) social context of collaborative and experiential learning, (ii) epistemology and ontology, facts and values, (iii) importance of reflection, and (iv) implications for student and faculty roles. Overall, this discussion aims to foster continued dialogue, discussion, and debate on the need for, and the role of, theory in IPE.