Anticoagulation clinics (ACs) have a greater impact on anticoagulation control than usual medical care (UMC). There is little evidence of the performance of AC in patients on warfarin living in low and middle-income countries. We sought to investigate the efficacy and safety of an AC in patients treated at a Brazilian public hospital. This was a randomized clinical trial that tested the efficacy of a recently implemented AC, compared to UMC, in outpatients with heart disease. The primary and secondary endpoints were time in the therapeutic range (TTR) and warfarin-related complications, respectively. Overall, 280 patients were enrolled and randomly assigned to Group A: one year at an AC (A1: first half-year; A2: second half-year); and Group B: first half-year receiving UMC (B1) and second half-year being assisted at the AC (B2). The mean age was 56.8 ± 13.1 years, and most patients were female (54.6%). Above 68% of patients had limited reading capability. A1 demonstrated greater TTR (62.4 ± 20.8%) than B1 (55.1 ± 28.5%) (p
= 0.014). Group B improved TTR from 55.1 ± 28.5% (B1) to 62.2 ± 23.1% (B2) (p
= 0.008). Despite the underpowered analysis of safety, A1 exhibited a lower incidence rate (IR) per patient-year (p-y) of total bleeding than B1 (incidence rate ratio (IRR): 0.78; p
= 0.041) and a reduction in intra-group comparisons (both groups: IRR 0.58; p
< 0.001). AC care helped increase TTR in a low-income setting showing favorable performance in a distinct population of those evaluated by previous studies. Extending AC care to similar populations may improve the outcomes of warfarin use.