In the present study thermoelectric properties of spark plasma sintered and subsequently air-annealed Sn_1-xSb_xO₂ (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 Sn_1-xSb_xO₂ 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 Sn_0.99Sb_0.01O₂.