Background: The active components of natural products provide a potential alternative to conventional immunotherapy for a variety of diseases conditions and become subject to scientific investigations currently worldwide. Objective: The purpose of this research was to investigate the immunostimulatory activity of the chitosan nanoparticle on Wistar albino rats. Materials and Methods: The present investigation was carried out on various groups of healthy adult rats. The assessment of immunomodulatory potential was carried out by neutrophil adhesion test, delayed-type hypersensitivity (DTH) response, haemagglutinating antibody (HA) titre, cyclophosphamide-induced myelosuppression and phagocytic activity were determined in various groups of animals. Results: The administration of chitosan nanoparticle at doses 300 mg/kg BW and 600 mg/kg BW but not at doses 150 mg/kg BW significantly increased in neutrophil adhesion fibers, haemagglutinating antibody titre values and potentiated the inhibited type hypersensitivity reaction induced by sheep red blood cells. Also, it had good response towards phagocytosis in carbon clearance assay and prevented myelosuppression of cyclophosphamide on rats. Conclusion: From these findings, it can be concluded that chitosan nanoparticle responsible for immunostimulatory activity and has therapeutic potential for the prevention of immune depressed conditions.