It has been demonstrated that chitosan nanoparticles can preserve fish fillets, which are very perishable, due to its ability to penetrate deep into its meat tissue and significant antimicrobial activity. The current study investigated the effects of chitosan nanoparticles at concentrations of 0.5%, 1%, and 2% on the shelf life of fresh tilapia fish fillets kept refrigerated. Furthermore, relying on hygiene indicators (total bacterial count, total psychrophilic count, and total mold and yeast counts), the effects of chitosan nanoparticles on enhancing the microbiological quality of tilapia fish fillets were examined. Additionally, the impact of the chitosan nanoparticles on certain foodborne pathogens, including Aspergillus flavus, Salmonella typhimurium and Staphylococcus aureus was investigated. The obtained results indicated that chitosan nanoparticles were effective in reducing the count of Salmonella typhimurium, Staphylococcus aureus and Aspergillus flavus but not able to eleminate such organisms completely until elapsing some days of storage depending on the used concentration of  chitosan nanoparticles used.