BACKGROUND: The prevalence of financial medication assistance (FMA), including patient assistance programs, coupons/copayment cards, vouchers, discount cards, and programs/pharmacy services that help patients apply for such programs, has increased. The impact of FMA on medication adherence and persistence has not been synthesized. OBJECTIVE: The primary objective of this study was to review published studies evaluating the impact of FMA on the three phases of medication adherence (initiation [or primary adherence], implementation [or secondary adherence], and discontinuation) and persistence. Among these studies, the secondary objective was to report the impact of FMA on patient out-of-pocket costs and clinical outcomes. METHODS: A systematic review was performed using MEDLINE and Web of Science. RESULTS: Of 656 articles identified, eight studies met all inclusion criteria. Seven studies examined FMA for medications treating cardiovascular diseases, while one study assessed FMA for cancer medications. Among included studies, FMA had a positive impact on medication adherence or persistence, and most measured this impact over one year or less. Of the three phases of medication adherence, implementation (5 of 8) was most commonly reported, followed by discontinuation (3 of 8), and then initiation (1 of 8). Regarding implementation, users of FMA had a higher mean medication possession ratio (MPR) than nonusers, ranging from 7 to 18 percentage points higher. The percentage of patients who discontinued medication was 7 percentage points lower in users of FMA versus nonusers for cardiovascular disease states. In one cancer study, FMA had a larger impact on initiation than discontinuation, ie, compared to nonusers, users of FMA were less likely to abandon an initial prescription (risk ratio= 0.12, 95% confidence interval [CI]: 0.08-0.18), and this effect was larger than the decreased likelihood of discontinuing the medication (hazard ratio = 0.76, 95% CI: 0.66-0.88). In 3 of 8 studies reporting on medication persistence, FMA increased the odds of medication persistence for one year ranged from 11% to 47%, depending on the study. In addition to adherence, half of the studies reported on FMA impacts on patient out-of-pocket costs and 3 of 8 studies reported on clinical outcomes. Impacts on patient out-of-pocket costs were mixed; two studies reported that out-of-pocket costs were higher for users of a coupon or a voucher versus nonusers, one study reported the opposite, and one study reported null effects. Impacts on clinical outcomes were either positive or null. CONCLUSIONS: We found that FMA has positive impacts on all phases of medication adherence as well as medication persistence over one year. Future studies should assess whether FMA has differential impacts based on phase of medication adherence and report on its longer-term (ie, beyond one year) impacts on medication adherence. DISCLOSURES: This work was sponsored by a grant from Pharmaceutical Research and Manufacturers of America (PhRMA). PhRMA had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Hung reports past employment by Blue Cross Blue Shield Association and CVS Health and a grant from PhRMA outside of the submitted work. Zullig reports research funding from Proteus Digital Health and the PhRMA Foundation. consulting fees from Novartis. Reed reports receiving research support from Abbott Vascular, AstraZeneca, Janssen Research & Development, Monteris, PhRMA Foundation, and TESARO and consulting fees from Sanofi/Regeneron, NovoNordisk, SVC Systems, and Minomic International, Inc. Bosworth reports research grants from the PhRMA Foundation, Proteus Digital Health, Otsuka, Novo Nordisk, Sanofi, Improved Patient Outcomes, Boehinger Ingelheim, NIH, and VA, as well as consulting fees from Sanofi, Novartis, Otsuka, Abbott, Xcenda, Preventric Diagnostics, and the Medicines Company. The other authors have nothing to report. This work was presented as a poster presentation at the ESPACOMP Annual Meeting in November 2020.