Background.To date, no research on the adherence of patients with atrial fibrillation (AF) within the territory of Kazakhstan and Central Asia has been conducted. Objectives. The study aimed to investigate the effect of a mobile application on adherence in patients diagnosed with AF and treated in outpatient clinics. In addition, the reliability of a structured scale for assessing adherence in patients with atrial fibrillation was also validated. Material and methods.A prospective one-centre study was conducted on 599 patients diagnosed with AF at the City Cardiology Centre (Almaty, Kazakhstan). Patients were sub-divided into control (CG) and intervention (IG) groups. Patients in the IG group used the MyTherapy mobile app. Treatment adherence was assessed using the 14-item Lebanese Drug Adherence Scale (LMAS-14). Data was collected before starting therapy (T1) and 3 months (T2), 6 months (T3) and 12 months (T4) after the start of treatment. Results. In the T1 period, the adherence of patients in the CG and IG groups was average (p = 0.547). After 3 months (T2), adherence of participants in the IG group (39.1 ± 1.3) was significantly higher than in the CG group (p ≤ 0.05). In the T3 period, patients of the IG group had a high adherence equal to 38.3 ± 1.6 (p ≤ 0.05). After 12 months (T4), the respondents in the IG group retained high adherence rates equal to 38.9 ± 3.2 (p = 0.001). An estimate of the readmission rate within 12 months shows relatively low rates in the IG group (9.8%). Conclusions. The results of the study showed the effectiveness of using the MyTherapy mobile app for increasing adherence in patients with AF. In addition, the use of the LMAS-14 facilitated and optimised the assessment of the level of adherence in patients with AF.