Objective: To evaluate the potential immunostimulant activity of glucosamine from Azadirachtaindica leaves in mice. Methods: The hexane, chloroform, methanol and aqueous extracts of Azadirachta indica leaves were prepared and its immunostimulant activity was studied. The aqueous extract of Azadirachta indica leaves (AEAIL) showed significant (P<0.001) higher immunostimulant activity than other extracts. Hence, isolation of possible phytoconstituent(s) from AEAIL was carried out and glucosamine was isolated. The Azadirachta indica leaves glucosamine (AILG) was administered at 266, 400 and 800 μg/kg of mice, intraperitoneal route weekly for 4 weeks to evaluate immunostimulant activity. The serum interleukin-2 (IL-2) level and histopathological studies on thymus were performed to confirm AILG immunostimulant activity. Results: The administration of above doses of AILG has significantly (P<0.001) increased serum IL-2 levels in mice than control mice. The dose dependent effect on IL-2 was noticed in AILG treated mice. The weight of thymus, liver and kidney were significantly (P<0.001) increased after the AILG treatments compared to control mice. Also, body weight of AILG treated mice showed significant (P<0.001) increment from second week to fourth week than control mice. The proliferation of T-lymphocytes in thymus after the administration of AILG was observed in histopathological study. Conclusion: The glucosamine was isolated from Azadirachta indica leaves aqueous extract and its immunostimulant activity was confirmed in mice.