Background: Adherence to medication is important for blood pressure control, which helps to reduce the risk of morbidity and mortality. The Blood Pressure Action Sheet (BPAS) was developed as a written material for supporting patients with hypertension. Objectives: to evaluate whether the BPAS would help to improve patient adherence to antihypertension medication. Methods: This was a mixed-method study; a pre–post interventional study was followed by a qualitative study to explore CHWs’ perspectives on the implementation of BPAS. Members of the Integrated Health Service Post for the Elderly (posyandu lansia), aged 45 years or older, and having stage 2 hypertension, were included in the study. The Medication Adherence Rating Scale (MARS) questionnaire was applied. Results: One hundred eight patients met the criteria for inclusion. Most were female (87%) and had a low education level. The average age was 67.2 ± 9.2 years. The MARS score was significantly higher after the intervention than before it (20.5 ± 3.4 vs 18.7 ± 4.5; p < 0.05). The percentages of patients categorized as completely adherent (score 24 or 25) were 11.9% before and 19.6% after the intervention. The percentages of non-adherent patients (score <20) decreased from 46.2% prior to the intervention to 21.6% three months later. CHWs perceived the BPAS as user friendly, useful, and applicable. The challenges for implementation relate to its use for illiterate patients. Conclusion: The 3-month implementation of the BPAS improved patients’ adherence to antihypertension medication. Despite the positive findings, the adherence after the intervention was still not optimal.