Thermoelectric (TE) materials have a promising application as they can interconvert thermal energy to electrical energy directly. Oxide TE materials have attracted more attention for this application due to their high temperature stability. In this work, In₂O₃(ZnO)₅ intrinsic superlattice ceramics with a layered structure were synthesized by reaction sintering a mixed powder of In₂O₃ and ZnO at 1200 °C for different holding times (t = 6, 8, 10, 12 and 15 h) in air. Their thermoelectric properties including the electrical conductivity, Seebeck coefficient and thermal conductivity, were measured from 323 to 973 K. The thermoelectric properties depended on the holding time. The highest ZT value of 0.19 at 973 K was obtained for the sample with a 12 h holding time.