This article examined the intervention fidelity strategies used and lessons learned in a translational study. In this study, the behavioral intervention was delivered within an existing clinical practice environment, outpatient cardiac rehabilitation (CR). The primary lessons learned were that the fidelity components of design, training, and delivery of the intervention were the most different from fidelity strategies used in typical intervention studies. The design component needed to take into account the unique characteristics of the clinical environments where the study was conducted and build these unique differences into the study design. Training and delivery of the intervention was different because existing CR staff delivered the intervention in this study; which is unlike typical intervention studies where research staff are trained to deliver the intervention. Monitoring receipt and enactment fidelity components were similar to monitoring in usual intervention studies probably because these components focus on monitoring the behaviors of the research participant. Translational research presents unique challenges and requires the development of a flexible and novel intervention fidelity plan tailored to a particular study.