The grain size and density of the sintered (Zn1 − xAlxO)mIn2O3 bodies decreased with the small Al2O3 content (≤ 0.012), and then increased gradually by further increasing the Al2O3 content. The addition of Al for Zn in the (ZnO)mIn2O3 led to an increase in both the electrical conductivity and the absolute value of the Seebeck coefficient. This indicates that the power factor was significantly enhanced by adding Al for Zn. The thermoelectric power factor was maximized to 1.67 × 10− 3 W m− 1 K− 2 at 1073 K for the (Zn0.992Al0.008O)mIn2O3 sample.