In this conceptual article, we draw on a graded theory concept as well as two exemplary cases to discuss the role of professional theorizing in teachers' practice. We present a model that can illustrate how a non-dichotomous, graded and processual understanding of theory may help overcome a split between theory, on the one hand, and practice, on the other. We argue that integrating theory and practice in this way may facilitate professional development and improve teachers' practice. An important part of this model is the notion of professional theorizing, which we define as a process where teachers reflect on, formulate, analyze, give rationales for and develop practice by means of theory of different degrees.