Polyaniline/expanded graphite (PANI/EG) composites with enhanced thermoelectric properties have been successfully synthesized by a simple ultrasonic mixing method with different EG contents. Their structure and morphology were investigated by XRD, SEM, and FTIR. Besides, thermal stability was investigated by TG analysis, which indicated that the PANI/EG composites exhibit better thermal stability than pure PANI. The PANI/EG composites show an interesting structure: PANI intercalates into the EG sheets and forms a sandwich structure. The thermoelectric properties of the samples were measured at room temperature. With the EG content increasing, the electrical conductivity and Seebeck coefficient were improved. As a result, a remarkably improved thermoelectric power factor was achieved. This work demonstrates a simple and effective method for improving the thermoelectric properties of conducting polymers. (C) 2015 Published by Elsevier B.V.