The contemporary focus on high fidelity implementation of researchbased practices often creates tensions for educators who seek to balance fidelity with needed flexibility as they strive to improve learner outcomes. In an effort to improve how decisions are made such that flexibility is achieved while fidelity to core components is maintained, this chapter begins with a discussion of the role of fidelity in research and practice. Particular attention is given to current conceptualizations of fidelity that may help inform theoretically and empirically driven adaptations to research-based practices. Specifically, we describe adaptations based on the instructional context for implementation and the characteristics of the individual learners. A framework for adapting research-based practices is then presented with relevant examples from research designed to optimize learner responsiveness without sacrificing fidelity to core components. The chapter ends with implications and future directions for research and practice.