The biological activity of chitosan aspartate particles formed in the chitosan‒L-aspartic acid‒water system at the initial stage of phase separation was investigated. Cultivation of Staphylococcus aureus 209 P and Escherichia coli 113-13 in the medium supplemented with our nanoparticles resulted in massive death of the bacterial cultures. The biocidal activity against gram-positive bacteria was most pronounced. Biological tests revealed high biocompatibility of our chitosan nanoparticles and their ability to accelerate the proliferative activity of the cultures of epidermal and epithelial cells. Our results indicate that our chitosan aspartate nanoparticles are promising for medico-biological and pharmaceutical applications.