Intervention fidelity is a key component of the design and conduct of physical therapy research, defined as ¿the methodological strategies used to enhance and monitor the reliability and validity of behavioral interventions.¿ This includes enhancing and assessing the extent to which an intervention is implemented as intended by its developers, including how they envisage the participants or patients to interact with the intervention. The authors of this Viewpoint focus predominantly on the fidelity of intervention delivery; highlight the importance of intervention fidelity for the physical therapy profession and its relevance for both physical therapy researchers and practitioners; and explore potential barriers to enhancing and assessing the fidelity of intervention delivery in physical therapy research.