Solution processed silicon-doped indium oxide, In-Si-O (ISO), thin-film transistors (TFTs) were fabricated on hydrophilic and hydrophobic substrates. A precursor solution fabricated via dissolving indium chloride and tetraethyl orthosilicate into solvents of acetonitrile and ethylene glycol was spin coated on the hydrophilic substrate. Annealing conditions were optimized, and the highest mobility of the ISO TFT increased to 8.1 cm2/Vs. We used another precursor solution by dissolving indium(III) isopropoxide and tetraethyl orthosilicate into a solvent of 2-(diethylamino)ethanol, and we fabricated ISO TFTs on the hydrophobic substrates. The highest mobility corresponded to 3.4 × 10−1 cm2/Vs.