BACKGROUND: Patients with cardiovascular disease need to adhere to their treatment and care recommendations to prevent the progression of their condition and improve their quality of life. In this regard, this study was conducted to develop a mobile application and test its effectiveness in improving medication adherence among persons with cardiac disease. METHODS: The study was conducted in two stages. The first stage involved the preparation of the "Mobile Application for Persons with Cardiac Disease" using the cascade model. In the second stage, 121 patients who were hospitalized in the cardiac intensive care unit of Ayatollah Taleghani Medical Education Center of Tehran from March to August 2023 were enrolled. The participants were randomly assigned to either the control group (63 people) or the intervention group (58 people). The study collected data using a medication adherence questionnaire on the 7th, 14th, and 21st day after discharge and compared the results with the control group. The data were analyzed using SPSS 20. RESULTS: The average age of the control group was 56.75 ± 11.38 years, and the average age of the intervention group was 57.03 ± 11.55 years. The comparison of the average medication adherence with independent t-tests showed a significant difference between the intervention and control groups on the 7th, 14th, and 21st day after discharge (P<0.01). The results of the repeated measures test in each group also showed that the difference between the groups increased over time (P<0.001). CONCLUSION: The results of the study showed that the mobile application is effective in improving medication adherence among heart patients.