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We report the effect of interface control using reduced graphene oxide (RGO) on the thermoelectric transport properties of Bi 2 Te 2.7 Se 0.3 (BTS)-RGO composites. The interface-controlled BTS-RGO composites were prepared by the consolidation of BTS-RGO hybrid powders using spark plasma sintering (SPS). The RGO-hybridization reduced the grain size in the BTS-RGO composites because the formation of an RGO network at the grain boundaries inhibited the grain growth during the SPS process. The carrier concentration was almost independent of the RGO content, however, mobility was reduced by the RGO network and it led to a decrease in the electrical conductivity of the BTS-RGO composites. Although the Seebeck coefficient was enhanced by the RGO-hybridization due to an increase in effective mass, the hybridization did not lead to an increase in the power factor of the BTS-RGO composites due to the reduction of the electrical conductivity. On the other hand, thermal conductivity was reduced significantly by the RGO-hybridization, and it led to the enhancement of ZT in the BTS-RGO composite. The effects of interface control using RGO on the thermoelectric transport properties of BTS-RGO composite are discussed in detail, and our results based on the RGO-hybridization strategy will be useful for developing thermoelectric materials with high ZTs.