Graphene aerogel was modified with polyaniline and Fe precursors to produce Fe/N/C catalysts for electrocatalytic oxygen reduction reaction in the acidic condition. The graphene aerogel was produced by a simple hydrothermal treatment of graphene oxide dispersion with a high surface area. Aniline was polymerized with the graphene aerogel powder, and the pyrolysis of the resulting material with FeCl3 produced Fe/N/C catalyst. The loading amount on the electrode and the catalyst ink concentration was carefully selected to avoid the mass transfer limitation inside the catalyst layer. The pyrolysis temperature affected the states of nitrogen sites on the catalyst; the sample prepared at 900 ℃ presented the highest mass activity. The sulfur was also doped with various amounts of FeSO4 with enhanced mass activity of up to 2.1mA/mg at 0.8 V in 0.5M H2SO4 solution. Its durability was also tested by repeating cyclic voltammetry in a range of 0.6-1.1V 5000 cycles. This graphene-aerogel-based carbon catalysts showed improved activity and durability for the oxygen reduction reaction in the acidic condition.