Sulfated chitosan (SC) can be used for such coating because of its similarity with heparin. The position of sulfate group incorporation in the chitosan chain is important for the improvement of its biological mechanism. The substitution of each reactive group of chitosan is required to increase the electrostatic repulsion between the sulfated films and blood proteins or platelets, and, thereby, reduce the thrombus formation. Moreover, the polymeric hydroxyl groups can activate the complement system through the alternative pathway. In this study, we developed SC films, with larger distribution of sulfate groups by substitution of three reactive groups in the chitosan chain to improve its hemocompatibility. Successful chemical modification confirmed the partially 2‐N‐3,6‐O‐SC. The hemocompatibility results showed decrease in bovine serum albumin and fibrinogen adsorption, platelet adhesion and an increase in the intrinsic pathway anticoagulant activity. Based on these results, partially tri‐SC can be considered suitable candidate for coating blood‐contacting medical devices. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47128.