The catalytic properties of rhodium complexes modified with oligoarylphosphonites were studied in the reaction of carbon dioxide hydrogenation to formic acid at room temperature. It was shown that oligoarylphosphonites, which are intermediate compounds between normal arylphosphines and aryl phosphites and can possess the properties of both phosphite and phosphine ligands simultaneously, are effective modifiers of rhodium complexes. The highest yield of formic acid was obtained at a molar ratio of P/Rh = 13 when the oligomer used was the condensation product of hydroquinone phosphorylation.