CHA2DS2VASc is the most widely used scheme to help improve rational indication of antithrombotic drugs for stroke prevention in patients with non-valvular atrial fibrillation. The objective of this study was to evaluate pharmacists’ role in rational use of antithrombotic drugs in patients with non-valvular atrial fibrillation. We conducted a retrospective cohort study comparing the rate of appropriate antithrombotic treatment between conventional practice and new practice with pharmacist intervention. Medical records of patients diagnosed with non-valvular atrial fibrillation and hospitalized from January to June 2013 (phase I without pharmacist intervention) and from December 2013 to May 2014 (phase II with pharmacist intervention) were included in this study to check the rational use of antithrombotic drugs based on CHA2DS2VASc scores. A total of 126 patients in the phase I and 106 patients in phase II were included. There was no statistically significant difference in CHA2DS2VASc scores between two phases. The proportion of patients who were appropriately prescribed antithrombotic drugs based on CHA2DS2VASc scores was significantly higher in phase II, compared to that in phase I (47.2% vs 22.2%, p=0.032). The intervention of the pharmacists could improve rational use of antithrombotic drugs in patients with non-valvular atrial fibrillation.