Ultrafine SmFeO3 powders were prepared by the thermal decomposition at 700°C of the corresponding hexacyanocomplex, Sm[Fe(CN)6]·4H2O. These powders were used for the preparation of pastes which were deposited as thick films on alumina substrates with comb-type Au electrodes. The films were fired at different temperatures in the 800-1000°C range. The content of α-terpineol, a component of the organic vehicle, was varied in the range 0.0046-4 wt%. The microstructure, the chemical composition at the surface, the electrical conductivity, and the NO2 sensing properties of the films were investigated. The content of α-terpineol strongly influenced the electrical conductivity and its activation energy. A significant reduction in the NO2 response was observed for the films containing smaller amounts of α-terpineol, together with an increase in conductivity. On the other hand, the largest NO2 response was observed for the films fired at 1000°C when 4 wt% of α-terpineol was used. Such increase in conductivity is attributed to a different oxygen surface layer on the SmFeO3 surface, which is induced by the decomposition reaction of α-terpineol during sintering. The materials processing parameters are thus of primary concern for the NO2 sensing properties of the SmFeO3 thick films. The correlations found between activation energy, NO2 sensitivity, and materials characteristics (influenced by the preparation parameters) are reported. These correlations can be used to design the gas-sensing properties of SmFeO3 thick films for the optimization of their sensing characteristics.