Objective: This study examined whether and to what extent researchers addressed intervention fidelity in research of after-school programs serving at-risk students. Method: Systematic review procedures were used to search, retrieve, select, and analyze studies for this review. Fifty-five intervention studies were assessed on the following components of intervention fidelity: strategies to enhance fidelity, measurement of fidelity, and use of fidelity data in data analysis and interpretation. Results: Of the 55 studies examined, only 55% reported well-defined intervention procedures, 42% used an intervention manual, 33% provided training on the intervention, 24% provided supervision for the implementers, 29% measured fidelity, only 4% used fidelity data in their analysis, and no studies reported the reliability of fidelity measures. Conclusion: Findings indicate an overall lack of attention to and reporting of intervention fidelity in after-school intervention studies. Implications for practice, policy, and research are discussed.