An improved process for the preparation of imatinib base and its pharmaceutically acceptable acid addition salts by (a) reacting 2-methyl-5-nitroaniline with cyanamide in the presence of hydrochloric acid to obtain 1-(2-methyl-5-nitrophenyl)guanidine hydrochloride; (b) converting 1-(2-methyl-5-nitrophenyl)guanidine hydrochloride to 1-(2-methyl-5-nitrophenyl)guanidine nitrate; (c) condensing 3-acetylpyridine with N,N-dimethylformamide dimethyl acetal to obtain 3-(dimethylamino)-1-(3-pyridinyl)-prop-2-en-1-one; (d) reacting 3-(dimethylamino)-1-(3-pyridinyl)-prop-2-en-1-one with 1-(2-methyl-5-nitrophenyl)guanidine nitrate to obtain N-(5-nitro-2-methylphenyl)-4-(3-pyridinyl)-2-pyrimidineamine; (e) reducing N-(5-nitro-2-methylphenyl)-4-(3-pyridinyl)-2-pyrimidineamine using hydrazine in the presence of Raney nickel to obtain N-(5-amino-2-methylphenyl)-4-(3-pyridinyl)-2-pyrimidine-amine; (f) condensing N-(5-amino-2-methylphenyl)-4-(3-pyridinyl)-2-pyrimidine-amine with 4-chloromethylbenzoyl chloride in the presence of an inorganic base to obtain 4-(chloromethyl)-N-(4-methyl-3-(4-(pyridin-3-yl)pyrimidin-2-ylamino)phenyl)benzamide; and (g) condensing 4-(chloromethyl)-N-(4-methyl-3-(4-(pyridin-3-yl)pyrimidin-2-ylamino)phenyl)benzamide with an excess of N-methylpiperazine to obtain imatinib base; and adding water or a mixture of water and an organic solvent; and isolating said imatinib base. The process allows for using simple starting materials, while simultaneously avoiding a laborious isolation and purification of intermediates and the final product, thereby facilitating scale-up.