FePt nanoparticles (NPs)/reduced graphene oxide (rG-O) composites have been synthesized using a one-pot strategy without surfactants. Monodisperse FePt NPs were homogenously loaded onto rG-O sheets. By controlling the concentration of dispersed graphene oxide (GO), uniform FePt flower-like nanoclusters can be obtained. FePt/rG-O composites exhibited exceptionally high electrocatalytic performance in the activity and durability for the oxygen reduction reaction (ORR), much superior to that of the commercial Pt/C (60%). The straightforward synthesis of FePt/rG-O composites provides a low-cost and high performance catalyst for the ORR, which is also a promising strategy for the synthesis of various Pt-based bimetallic alloy/rG-O composites for potential uses in catalysis and energy fields.