Although chronic anticoagulation is commonly prescribed to prevent thrombosis and malfunction of hemodialysis tunneled cuffed catheters (TCC), there are only limited data regarding its efficacy. The aim of this prospective study was to evaluate whether anticoagulation with adjusted-dose warfarin targeting an international normalized ratio (INR) of 1.5-2.0 is associated with improved catheter outcome in long-term patients at high risk of TCC malfunction. Among the 65 patients included in the study, 35 were considered at high risk (i.e., patients with a history of previous TCC thrombosis requiring catheter replacement and/or with TCC malfunction occurring within 2 weeks after catheter insertion in the absence of mechanical problems) and were prescribed warfarin, whereas 30 low-risk patients did not receive anticoagulation. During follow-up, TCC malfunction, defined as the need for inversion of catheter lines and/or recombinant tissue-type plasminogen activator infusion, was observed in 61.5% of patients. Among patients receiving warfarin, 19 (54.3%) achieved adequate anticoagulation (i.e., > 80% of follow-up INR values and INR value at the time of malfunction within target range). Anticoagulation was considered inadequate in 16 patients (45.7%). Malfunction-free catheter survival at 9 months was 47.1% in patients with adequate anticoagulation compared with 8.1% in patients with inadequate anticoagulation (p = 0.01). This difference remained statistically significant after adjustment for aspirin intake. These results suggest that achieving adequate anticoagulation with target INR 1.5-2.0 may prevent TCC malfunction and improve catheter outcome.