A simple, one-pot route was developed for the synthesis of SnO2-reduced graphene oxide (RGO) composites. Simultaneous reduction of graphene oxide (GO) and heterogeneous nucleation and growth of SnO2 on the surface of RGO under the supercritical methanol medium resulted in uniform deposition of well-dispersed SnO2 nanoparticles on the RGO sheets. In comparison with the bare SnO2 nanoparticles and bare RGO sheets, the as-synthesized SnO2-RGO composites exhibited enhanced Li-ion storage and high rate performance. The SnO2-RGO composite with a SnO2 loading of 58 wt% delivered a reversible discharge capacity of 776 mAh g−1 after 70 cycles at a current density of 0.1 A g−1 and a rate performance of 147 mAh g−1 at a high current density of 5 A g−1. In addition, after 1000 continuous cycles at 1 A g−1, the composite electrode exhibited a reversible discharge capacity as high as 531 mAh g−1 with excellent capacity retention. The enhanced long-term cyclability and high-rate performance of the SnO2-RGO composite can be attributed to the effective confinement of SnO2 nanoparticles on the RGO sheets, and thus, the interparticle agglomeration and volume change associated with alloying–dealloying of SnO2 during cycling can be prevented and cell integrity can be maintained.