Background Community pharmacists can play an important role in optimizing warfarin treatment, which is very important in vulnerable patient groups such as the elderly patients in rural areas. Objective To evaluate the impact of a community pharmacist’s interventions on the quality of anticoagulation in elderly rural patients receiving warfarin. Setting A community pharmacy in Donji Miholjac in Croatia’s province of Slavonia. Method We conducted a prospective randomized trial. Eligible patients were recruited at the pharmacy and randomized into two groups. All participants were followed up monthly for a period of 6 months. Repeated education and a follow up plan were provided to the participants in the intervention group, and their general practitioners were contacted to correct the warfarin dose or to avoid drug interactions. Main outcome measure Time in therapeutic range (TTR) calculated by the Rosendaal method. Results A total of 140 patients were randomized and 131 patients finished the study, 65 patients in the intervention group. Median age was 73 years. At the end of the follow-up period, the median TTR was significantly higher in the intervention group (93 vs. 31.2% for intervention and control, respectively; P  < 0.001). The proportion of patients with TTR ≥ 65% was also significantly higher in the intervention group (86.2 vs. 7.6% for intervention and control, respectively; P  < 0.001). Factors independently associated with TTR ≥ 65% were intervention ( P  < 0.001), less frequent dose change ( P  = 0.005), better adherence ( P  < 0.001) and less variable vitamin K intake ( P  = 0.010).