Background/Context: In many countries, there are multiple studies intended to improve initial teacher education. These have generally focused on pieces of teacher education rather than wholes, and have used an underlying linear logic. It may be, however, that what is needed are new research questions and theoretical frameworks that account for wholes, not just parts, and take complex, rather than reductionist perspectives. Purpose: This article examines the challenges and the promises of complexity theory as a framework for teacher education research. One purpose is to elaborate the basic tenets of complexity theory, summarize its previous uses, and identify key challenges. A second purpose is to propose a new research platform that combines complexity theory with critical realism (CT-CR) and prompts a new set of empirical questions and research methods. Research Design: Drawing on scholarship from sociology and education, the underlying design--or logic--of this analytic essay is this: explanation of the basic tenets of complexity theory applied to teacher education, assessment of previous research informed by complexity theory, response to the major epistemological and methodological challenges involved in using complexity theory as a research framework, and proposal of a new set of questions and methods. Findings/Results: Complexity theory is appealing to teacher education researchers who want to avoid simplistic and reductionist perspectives. However, most previous complexity research has not addressed the critiques: the proclivity of complexity theory for retrospective description; the assertion that, given its rejection of linear causality, complexity theory cannot provide causal explanations with implications for practice; and the charge that complexity-informed research cannot deal with the values and power inequalities inherent in the normative enterprise of education. Integrating complexity theory with critical realism provides a way to address these fundamental challenges. Building on this new platform, the essay proposes a new set of empirical questions about initial teacher education along with several innovative research methods to address those questions. Conclusions/Recommendations: This essay concludes that the combination of complexity theory and critical realism offers a unique platform for teacher education research, which has theoretical consistency, methodological integrity, and practical significance. The essay recommends that its proposed new empirical questions and methods may have the capacity to show us where to look and what processes to trace as teacher candidates learn to enact practice that enhances the learning of all students, including those not well-served by the current system.