Reduced graphene sheets (RGSs) were prepared via hydrazine reduction of exfoliated graphite oxide and their morphology was characterized by atomic force microscopy. The electrocatalytic reduction of oxygen (O2) with RGSs was studied by cyclic and rotating risk electrode voltammetry using RGSs-modified glassy carbon electrodes in alkaline media. The results show that this modification with RGSs makes the peak potential shift in the positive direction and increases the peak current. The kinetics study shows that the numbers of electrons transferred for the oxygen reduction reaction are ca. 3 at potentials of the first reduction wave, indicating the peroxide produced can transfer into OH–.