Chemically modified graphene has been studied in many applications due to its excellent electrical, mechanical, and thermal properties. Among the chemically modified graphenes, reduced graphene oxide is the most important for its structure and properties, which are similar to pristine graphene. Here, we introduce an environment-friendly approach for preparation of reduced graphene oxide nanosheets through the reduction of graphene oxide that employs L-cysteine as the reductant under mild reaction conditions. The conductivity of the reduced graphene oxide nanosheets produced in this way increases by about 10(6) times in comparison to that of graphene oxide. This is the first report about using amino acids as a reductant for the preparation of reduced graphene oxide nanosheets, and this procedure offers an alternative route to large-scale production of reduced graphene oxide nanosheets for applications that require such material.