The oriental traditional medicine, Aruncus dioicus var kamtschaticus (ADK) is used for hemostasis (blood stopping) and the promotion of blood circulation. Recently, the demands of the aerial part of ADK as edible mountain herbs are rapidly increased due to its unique fragrance and bioactivity. In this study, to evaluate the anti-thrombosis activity of ADK, ethanol extract and organic solvent fractions were prepared from aerial parts of ADK, and their anticoagulation and anti-platelet aggregation activities were determined. In an anticoagulation activity assay, the ethanol extract of ADK increased the thrombin time, prothrombin time, and activated partial thromboplastin time (aPTT) 1.4-2.3 times at a concentration of 5 mg/ml. Among the fractions, the ethylacetate fraction showed strong inhibitory effects against blood clotting factors, as shown in an extension of the aPTT. In contrast, the butanol fraction strongly promoted blood clotting. In an anti-platelet aggregation assay, the activity of the ethanol extract was comparable to that of aspirin, a commercial anti-platelet aggregation agent, and the butanol fraction showed 2-fold higher aggregation inhibitory activity than aspirin. The aforementioned ethanol extract and active fractions have ignorable hemolytic activity against human red blood cells up to a concentration of 0.5 mg/ml. Considering the high content of total polyphenol, total flavonoid, and total sugar of the ethylacetate and butanol fractions, the purified active substances have potential as safe and novel anti-thrombosis agents. This report provides the first evidence of anti-thrombosis activity of ADK.