This invention relates a method for the preparation of platinum(II) oxalato complexes from their dihalogenoplatinum(II) precursors having either neutral monodentate or bidentate non-leaving co-ligands. Of particular interest is oxaliplatin. The method includes the step of reacting a halogenoplatinum(II) complex containing a neutral monodentate or bidentate ligand with an oxalate in a non-aqueous solvent or a mixed solvent system. The mixed solvent system is solvent mixture containing a non-aqueous solvent and water. According to the present invention, the non-aqueous solvent is an alcohol.