Alkylated derivatives of low molecular weight chitosan with different substitution degrees of 98, 40, and 9% (I, II, and III respectively) have been synthesized. The structure of the obtained derivatives was defined by spectral assays (IR-spectroscopy and proton magnetic resonance). Chitosan derivatives were characterized with positive zeta-potential (33–51 mV) and solubility from 2 to 100 mg/mL in pH 7.4 and 25°C. It was shown that, at a concentration of 0.0014–0.0029 mg/mL, derivative I, as well as protamine sulfate, could be used to neutralize the anticoagulant activity of unfractionated or low molecular weight heparin. At a concentration of 0.0029–0.58 mg/mL, derivative I enhanced platelet aggregation, which would be necessary when hemostatic compounds or materials were used. Derivatives II and III enhanced platelet aggregation to a lesser extent.