Measuring the extent to which an intervention is implemented with fidelity (ie, as intended) is critical to its success. Comprehensive medication management (CMM) is an established pharmacy practice intervention in outpatient settings. However, there is no standardized approach to measuring its implementation fidelity. This article describes a fidelity assessment system that includes measures and tools for use by pharmacists and others involved with the practice of CMM. This system is a comprehensive but modular approach to assessing fidelity designed to facilitate measurement along three fidelity dimensions: context (ie, infrastructure needed to support CMM), content (ie, adherence to CMM), and competence (ie, skillset needed to deliver CMM). Practical recommendations with examples are also provided to facilitate application of the system in real‐world settings. These recommendations are designed to assist with prioritization of the fidelity dimensions to consider timing of the assessments, use of the resulting data, interpretation of the data, and translation of results into actionable decisions. Incorporating fidelity measurement into any CMM implementation effort is key to ensuring consistent care delivery and impactful clinical outcomes.