The present research deals with formulation of microspheres containing an Anti-cancer drug Imatinib mesylate reduce the frequency of dosing. It is a protein-tyrosine kinase inhibitor, especially useful in the treatment of various types of cancer and can also be used for the treatment of atherosclerosis, thrombosis, restenosis, or fibrosis. Imatinib mesylate loaded microspheres were formulated by using both hydrophilic and hydrophobic polymers by Chemical Cross Linking method with Chitosan, and Ethyl Cellulose to develop a sustained release dosage form. The effect of concentration of cross-linking agent (Glutaraldehyde) on the microspheres properties like percentage of drug loading, biodegradability, drug release kinetics, particle size, encapsulation efficiency, angle of repose, bulk density, SEM, DSC and XRD were investigated in our study. Moreover, the kinetics of Imatnib mesylate released from different formulations of microspheres were analyzed using four different theoretical models, that is, Zero order, First order, Peppa's, and Higuchi models. Microspheres prepared with Glutaraldehyde showed different release kinetics. Increasing the polymer concentration decreased the release rate of Imatinib Mesylate from microspheres because of formation of greater structural strength and more tightly texture with the drug. Besides, microspheres gave an adequate fit to either zero order or first order kinetic models, depending on the extent of cross linking reaction between drug and the cross linking agent. © RJPT All right reserved. © 2012 Elsevier B.V., All rights reserved.