A 20-year-old woman with ulcerative colitis flare was admitted to Fukui Red Cross Hospital. During treatment with granulocyte and monocyte apheresis (GMA), the patient complained of chest discomfort and was diagnosed with pulmonary thromboembolism with central intravenous catheter thrombosis. Apixaban, a direct oral anticoagulant (DOAC), was used as monotherapy for anticoagulation, and thromboembolism was resolved without complication. Among extraintestinal complications in patients with ulcerative colitis, pulmonary thromboembolism can be a life-threatening condition and requires prompt anticoagulant therapy. Although the effectiveness of conventional pharmacological anticoagulation using warfarin and heparin has been reported, the efficacy of DOAC monotherapy remains controversial. DOAC monotherapy may be considered and innovative therapeutic strategy for a thromboembolic condition in patients with ulcerative colitis.