Nitrogen-doped functionalized graphene nanosheets (N-fGNS) were synthesized by a simple and green method and used for the visible-light-driven water splitting. Under visible light irradiation, N-fGNS produced H2 and O2 (1380 and 689 μM g-1 h-1, respectively) efficiently without co-catalysts. The excellent photocatalytic water splitting performance of N-fGNS is attributed to nitrogen doping and abundant surface defects as active sites.