Introduction <p>Adherence to antihypertensive medications is essential to ensure therapeutic effectiveness. However, the long-term clinical impact of adherence during the first year of treatment in elderly patients remains uncertain.</p> Aim <p>To evaluate the level of adherence to antihypertensive therapy during the first year following diagnosis in elderly patients and to assess its long-term clinical implications.</p> Methods <p>This retrospective cohort study included adult patients aged ≥ 65 years with newly diagnosed essential hypertension. Medication adherence during the first year after diagnosis was assessed using the proportion of days covered (PDC). Clinical outcomes—including myocardial infarction, stroke, and all-cause mortality—were evaluated beyond the first year, with an average follow-up of 108 months. Data were extracted from the electronic medical records of a large community-based healthcare provider.</p> Results <p>A total of 2934 patients were included in the analysis. The mean age was 72.4 years, and approximately 60% were women. Among the cohort, 21.3% had a PDC of less than 70%. Adherence above the 70% threshold was significantly associated with a reduced incidence of stroke (HR = 0.59; 95% CI 0.37–0.94; <i>p</i> = 0.028).</p> Conclusions <p>Higher adherence (≥ 70%) to antihypertensive therapy during the first year of treatment in elderly patients was associated with a significantly lower incidence of stroke in subsequent years. These findings highlight the importance of early adherence and support the need for targeted interventions to promote sustained medication use, even in older populations.</p>