Hemorrhage is the leading cause of preventable death in military conflicts. Different types of hemostatic dressings have been compared in animal studies for their ability to control bleeding. However, the effects of hemostatic agents in animals may be different from those in humans. The aim of this study was to assess the efficacy of hemostatic dressings in human blood. Clotting time, clot formation time, α-angle, maximum clot firmness, and lysis index of human blood incubated with QuikClot Gauze, Celox Gauze, QuikClot ACS+, and standard gauze, were compared using rotational thromboelastometry (ROTEM). Nonactivated, intrinsically activated, extrinsically activated, and fibrin-based ROTEM were used to elucidate different mechanisms of action of those dressings. QuikClot Gauze was the most efficacious hemostatic dressing, followed by Celox Gauze and standard gauze. QuikClot ACS+ was clearly outperformed. Modern hemostatic dressings such as QuikClot Gauze and Celox Gauze should be preferred to previous generations of hemostatic dressings, such as QuikClot ACS+. In vitro studies like ROTEM can provide valuable information about the mechanisms of action of hemostatic dressings. A combination of different mechanisms of action may increase the efficacy of hemostatic dressings.