Few studies have assessed the fidelity of practice facilitation (PF) as an implementation strategy, and none have used an a priori definition or conceptual framework of fidelity to guide fidelity assessment. The authors adapted the Conceptual Framework for Implementation Fidelity to guide fidelity assessment in HealthyHearts NYC, an intervention that used PF to improve adoption of cardiovascular disease evidence-based guidelines in primary care practices. This study provides a model that practice managers and implementers can use to evaluate fidelity of PF, and potentially other implementation strategies.