A 77-year-old man with colon cancer and multiple metastases to the liver and lungs underwent resection of the primary tumor and D3 lymph node dissection. He presented with chronic atrial fibrillation; therefore, warfarin was used initially as an anticoagulant. Because of the need to administer a fluoropyrimidine-based antineoplastic agent[5-fluorouracil(5-FU)] during chemotherapy, we changed the anticoagulant from warfarin to dabigatran etexilate(dabigatran)before initiating chemotherapy. No complications or excessive decrease in coagulability was observed after changing the anticoagulant; chemotherapy was safely continued. Unlike warfarin, dabigatran undergoes renal excretion, and thus, can be safely used in anticoagulant therapy without any drug interaction with 5-FU. Thus, we believe that dabigatran may be the anticoagulant of choice in the future for cancer patients who are scheduled to undergo chemotherapy using fluoropyrimidine-based antineoplastic agents.