The present inventiin discloses pharmaceutically acceptable salts of imatinib of Formula (II) wherein in S represent the acid selected from the group consisting of oxalic acid, p-toluene sulfonic acid, naphthalene sulfonic acid, benzene sulfonic acid, nitric acid, phosphoric acid, acetic acid, maleic acid, fumaric acid, amino acids like lysine, lysine HC1, arginine which forms a salt with imatinib.