In the present study thermoelectric properties of spark plasma sintered and subsequently air-annealed Sn1-xSbxO2 (x = 0, 0.01, 0.03, 0.05) ceramic samples were characterized. It was observed that addition of Sb greatly affects density, microstructure and thermoelectric properties of SnO2. Grain size decreases and the microstructure becomes more homogeneous with increasing Sb content in the Sn1-xSbxO2 samples from x = 0.01 to 0.05. The thermal conductivity and Seebeck coefficient of the Sb doped samples decreases with an increase in Sb concentration, while electrical conductivity increases up to a maximum at Sb doping level of x = 0.03 and then decreases at x = 0.05. The highest thermoelectric figure of merit of ZT ≈ 0.06 at 1073 K was exhibited by the sample of composition Sn0.99Sb0.01O2.