BACKGROUND: Warfarin has a narrow therapeutic window. Maintaining the patient's international normalized ratio (INR) within a predefined therapeutic range is one of the main challenges of warfarin treatment. This study aimed to compare the INR values of patients followed by face-to-face and telephone applications. METHODS: This study was designed as a randomized controlled trial. Twelve patients living in a distant place were assigned to the experimental group, and 12 patients living nearby and followed-up in the outpatient clinic were assigned to the control group. A Patient Information Form and the Adherence to Refills and Medications Scale were used to collect data. RESULTS: There was no significant difference between the groups in terms of demographic and clinical characteristics except for age (P > .05). The INR values of 67% of the patients followed in the outpatient clinic and 72% of the patients followed with the application were in the therapeutic range. There was no significant difference between the groups and medication adherence was high in both groups (P > .05). CONCLUSION: In light of the findings of our study, which demonstrated that the INR levels of patients who were monitored both face-to-face and via a telephone application were within the same therapeutic range, it was concluded that the telephone application can be used to manage warfarin therapy.