Chitosan, a non-toxic and biodegradable compound, enhances plant growth and secondary metabolite production, presenting innovative approaches to mitigating plant stress. Salinity, a common abiotic stress, significantly impairs plant growth and development. This study investigates the effects of chitosan on the physiological, biochemical, and gene expression responses of salt-stressed Brassica napus L. exposed to NaCl concentrations of 0, 50, 100, and 150 mM. Chitosan was applied as a foliar spray at concentrations of 0, 5 and 10 mg/L. The research focuses on gene expression changes in P5CS, PIP, and PAL genes in the roots and shoots of Brassica napus, revealing notable alterations, particularly in PIP expression under saline conditions. The study also observed enhanced PAL enzyme activity, increased chlorophyll and proline levels, and changes in iron, potassium, and nitrogen content. These findings demonstrate chitosan's potential to improve plant resilience to salt stress. By modulating gene expression and enhancing physiological responses, chitosan presents a promising solution for enhancing plant tolerance to salinity, with valuable implications for agricultural practices.