A facile and scalable process was developed for the synthesis of single-layer MoS2–graphene nanosheet (SL-MoS2–GNS) composites based on the concurrent reduction of (NH4)2MoS4 and graphene oxide sheets by hydrazine in the presence of cetyltrimethylammonium bromide (CTAB), followed by annealing in a N2 atmosphere. The morphology and microstructure of the composites were examined by X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy and Raman spectroscopy. The formation process for the SL-MoS2–GNS composites was also investigated. The SL-MoS2–GNS composites delivered a large reversible capacity and good cycle stability as a Li-ion battery anode. In particular, the composites easily surpassed MoS2 in terms of rate performance and cycle stability at high current densities. Electrochemical impedance spectroscopy revealed that the GNS in the composite not only reduced the contact resistance in the electrode but also significantly facilitated the electron transfer in lithiation and delithiation reactions. The good electrochemical performance of the composites for reversible Li+ storage could be attributed to the synergy between the functions of SL-MoS2 and GNS.