This article provides a review of theoretical approaches to model-based learning and related research. In accordance with the definition of model-based learning as an acquisition and utilization of mental models by learners, the first section centers on mental model theory. In accordance with epistemology of modeling the issues of semantics, ontology, and learning with models as well as structural aspects and functions of mental models (such as simplification, idealization, analogy, simulation) will be discussed. Starting with early theoretical approaches in the realm of cognitive science, the emphasis will be on recent theoretical developments in the field of reinforcement learning that distinguish between model-based and model-free learning. These new theoretical approaches confirm, to a large extent, the early theories of mental models but they also contribute new insights in age-related aspects of model-based learning. The second main section of the article provides a review of basic and applied research on model-based learning. A short overview of basic research on mental models aims at sketching an "overall picture" followed by a more detailed description and discussion of findings in the field of instructional research, especially with regard to K-12 STEM education and the support of model-based learning through teaching and technology.