The aim of this work was a comprehensive study of the oxidative and sorptive properties of a hybrid polymer containing manganese oxide toward As(III) and As(V). A poly(styrene-divinylbenzene) copolymer containing oxidative functional groups (SO2NBrNa) was used as the supporting material for MnO2. The inorganic component was deposited as a result of the oxidation reaction of Mn(II) with oxidative groups of the host polymer. The surface of the polymer matrix was evenly covered with a thin layer of manganese oxide. The obtained product (R/S/Mn) exhibited high oxidative capacity over a wide pH range (2–12); however, under acidic and neutral conditions, the reaction ran significantly faster. The studied material shows some sorption properties but its sorption capacity is much lower than its oxidation capacity. The treatment, in a column regime, of the arsenic solution containing 1 mg As(III) dm−3 and coexisting ions in concentrations similar to those in natural waters, confirmed the excellent oxidation capacity of the obtained product. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39489.