Significance: Selective inhibition of the intrinsic coagulation pathway is a promising strategy for developing safer anticoagulants without serious bleeding consequences. We prepared and identified a series of oligosaccharides as inhibitors of the intrinsic tenase, which is the final and rate-limiting enzyme complex in the intrinsic coagulation pathway and is an attractive but less explored target for anticoagulants due to the lack of a pure selective inhibitor. Analysis of these purified oligosaccharides reveals the precise structure of fucosylated glycosaminoglycan. Among these oligosaccharides, nonasaccharide is the minimum fragment that retains potent anticoagulant activity by selective inhibition of the intrinsic tenase while avoiding adverse effects and, thus, it may pave the way for the development of better treatments for thromboembolic diseases.