Abstract To evaluate the effectiveness of an anticoagulation protocol adapted in a mobile application (appG) for patients using warfarin. This was a cluster randomized controlled clinical trial carried out in basic health centers of Ijui, RS, Brazil, between April and October 2017. The appG was installed on the cell phones of all physicians belonging to the intervention group. Primary outcomes were bleeding and thrombosis, and secondary outcomes were changes in the dose of warfarin, use of new drugs, drug interactions, search for health services, and remaining on the target international normalized ratio. Thirty-three patients belonging to 11 basic health centers were included in this study. From these, 15 patients were in the intervention group which used the appG, and 18 were in the control group. After 6 months, patients in the appG group had fewer bleeding events (7% versus 50%, p-value=0.028) and a lower weekly dose of warfarin (29.3 ± 9.7 mg versus 41.7 ± 12.5 mg, p-value=0.030) when compared to the control group. The anticoagulation protocol adapted in a mobile app reduced bleeding in patients using warfarin.