Kareish cheese is the most famous soft cheese in Egypt. The distinctly nutritious nature makes them accurate media for bacterial growth during processing, it is hard to produce milk free from microbes therefore, the microbial content of milk is a crucial feature in figuring out its quality.so the effect of different concentrations of chitosan nanoparticles on some pathogenic microbes like Escherichia coli and aspergillus flavus could be determined. Different concentrations of chitosan nanoparticles (CSNPs) were utilized to improve the bacterial condition of made kareish cheese during storage at cold temperatures (2.5%, 5% and 10%). After being inoculated with E. coli and Aspergillus flavus, cheese samples were treated with various doses of chitosan nanoparticles and stored at 4°C. According to the findings, (CSNPs) (10%) had the greatest influence on the inoculated microbial count in cheese samples, followed by CSNPs (5%) and (2.5%). It may be inferred that chitosan nanoparticles (CSNPs) have an antimicrobial action against these species, which is amplified by increasing CSNps concentration. As conclusion we suggest using chitosan nanoparticles to preserve kareish cheese