Non-vitamin K antagonist oral anticoagulants (NOACs) have been widely used for the prevention of ischemic strokes in patients with nonvalvular atrial fibrillation (AF). At present, NOACs have been evaluated for the treatment of deep vein thrombosis (DVT). We examined the efficacy of dabigatran, the first NOAC for anticoagulation of AF in Japan, in outpatients who suffered from DVTs under a deteriorated general condition.Thirty-six consecutive outpatients diagnosed with DVT at our institute were enrolled. Not all patients could be hospitalized due to other clinical problems; 15 (42%) had malignant tumors, 9 (25%) psychological disorders, and 6 (17%) postoperative orthopedic disease. Dabigatran was administered at a dose of 110-150 mg once or twice daily, depending on the renal function and age. The mean dosage of dabigatran was 211.7 ± 36.6 mg per day. In 18 (50%) patients, the DVTs were completely dissolved and disappeared over a treatment term of 4.3 ± 4.3 months. In 9 patients (25%), the DVTs partly dissolved, but in the remaining 9 (25%) patients, dabigatran was totally ineffective. During a follow-up of 30.5 ± 5.3 months, DVTs did not recur with dabigatran in 18 patients with an effective efficacy. In a multivariate analysis, patients with small sized thromboses and those without malignant tumors were significantly associated with the DVTs dissolving (P = 0.003 and P = 0.006, respectively).Dabigatran was effective for dissolving DVTs in outpatients with a poor condition, particularly when the size of the DVT was small and malignant tumors were absent.