Sodium carboxymethyl cellulose (Sol-CM) is a water-soluble material derived from plants. The molecular mass of Sol-CM is estimated approximately 170 kDa. In our previous study, we found that Sol-CM were able to hemostatic effects in animals. The Sol-CM was found to enhance polymerization of fibrin monomers in a concentration-dependent fashion, without stimulating the activation of proenzymes, such as prothrombin, that are involved in the blood coagulation process. Fibrin fibers that formed in the presence of Sol-CM appeared to be thicker than those formed in its absence and Sol-CM was incorporated into them in the scanning electron microscopic study. Sol-CM promoted fibrinogen gamma-chain cross-linking mediated by activated blood coagulation factor XIII and also plasminogen activation by tissue-type plasminogen activator bound to fibrin. These results suggested that Sol-CM accelerated fibrin aggregation by hastening of D-D self-association of fibrin monomers at the stage of two-stranded fibrin protofibril formation as well as lateral association between two-stranded fibrin protofibrils. Sol-CM also restored polymerization of abnormal fibrinogen whose fibrin polymerization was inhibited by abnormal D-D self-association. These findings showed that the hemostatic effects of Sol-CM were due to acceleration of fibrin polymerization.