Palladium-doped mixed particles of tin oxide and aluminum oxide were prepared by spray pyrolysis using filter expansion aerosol generator. The effect of palladium and alumina on the crystallinity and morphology of tin oxide particles was investigated. The crystal growth of tin oxide was retarded by doping of palladium. The particles were submicron in diameter and had spherical morphology. Submicron size particles consisted of several nanometer size primary particles, and had hollow and porous morphology. The BET surface areas of tin oxide particles were slightly increased when palladium and alumina was separately added to the tin oxide particles, while the BET surface areas of tin oxide particles were decreased when palladium and alumina were added together. The mixed particles prepared from aluminum isopropoxide as aluminum source had higher BET surface area than that prepared from aluminum nitrate. The dispersion of palladium in the mixed particles was 19%.