["Journal of the American Geriatrics Society, Volume 74, Issue 6, Page 1756-1770, June 2026. ", "\nABSTRACT\n\nIntroduction\nThe Age‐Friendly Health Systems (AFHS) initiative aims to improve care for older adults through the “4Ms” framework: What Matters, Medication, Mentation, and Mobility. Despite national momentum and evidence within individual M domains, limited evidence guides outpatient AFHS implementation of the 4Ms as a set. The objective of this systematic review was to summarize the evidence of the impact of AFHS implementation in outpatient settings.\n\n\nMethods\nWe searched Medline, EMBASE, CINAHL, Cochrane, and clinicaltrials.gov from 2015 to November 22, 2024. Comparative studies that implemented all 4Ms in outpatient settings were included. Risk of bias was assessed using questions derived from the Cochrane Risk of Bias tool for RCTs and the Risk of Bias In Non‐randomized Studies—of Intervention tool for other study designs, and results were summarized using GRADE methodology.\n\n\nResults\nTwelve US‐based studies met inclusion criteria. Overall, implementing AFHS interventions was associated with improved process measures across all 4Ms, though the effectiveness of specific implementation strategies could not be determined. Outcome and structural measures were infrequently reported. Study heterogeneity and poor reporting limited generalizability.\n\n\nDiscussion\nFindings underscore the urgent need for standardized, outcomes‐oriented AFHS measurement before policy and payment reforms, such as CMS's Age‐Friendly Hospital Measure, are expanded into outpatient settings. To advance meaningful transformation, future research must prioritize implementation fidelity, outcome evaluation, and measures that reflect older adults' values and lived experiences.\n\n"]