To provide a primer regarding treatment fidelity as it affects evidence-based practice (EBP) for speech-language pathologists.This tutorial defines treatment fidelity, examines the role of treatment fidelity for speech-language pathologists, provides examples of fidelity measurement, and describes approaches for assessing treatment fidelity.Treatment fidelity is a neglected construct in the EBP literature; however, fidelity is a crucial construct for documenting intervention effectiveness and engaging in EBP.