OBJECTIVES: Adhering to prescribed medications is crucial for patients with chronic diseases to manage their conditions. However, rates of adherence to maintenance medications are often suboptimal, and forgetfulness is one of the most common reasons cited for nonadherence. Our objective is to evaluate the impact of an email refill reminder system on patient adherence to medications used to treat chronic conditions. METHODS: This retrospective cohort study used a propensity score matched (PSM) control group. Patients who received email refill reminders the first time in April 2013 comprised the test group. The control group included patients who did not receive the reminders and were propensity matched 1:1 to the test group based on baseline characteristics of age, gender, medications, patient fill status, baseline adherence rate, and therapeutic class. Medication adherence and persistence were calculated and compared between test and control groups in a 12-month follow-up period. Medication adherence was evaluated using continuous and categorical proportion of days covered (PDC) measures. Medication persistence was measured using days on therapy (persistence) and percent of patients on therapy.  RESULTS: After PSM, test and control group included 14,527 patients each and their baseline characteristics were comparable. One-year PDC for patients in the test group was 2.59% higher compared to the control group (51.15% vs. 48.56%, P < .001). Persistence for the test group was 7.90 days higher than in the control group (236.01 vs. 228.11, p< .001). At the one-year follow-up, 43.79% of patients in the test group stayed on their therapy compared to 40.99% in the control group (P<. 001). CONCLUSIONS: Patients receiving email refill reminders demonstrated better adherence and persistence to maintenance medications than patients who did not receive the reminders.