In this study, we fabricated zinc tin oxide (ZTO) thin-film transistors (TFTs) using a sol–gel solution at an annealing temperature of 350 °C. We used a precursor combination of alkoxide and metal chloride to utilize the alkyl halide elimination reaction. Compared with transistor using chloride-only precursors, the resulting ZTO transistor showed improved performance. Solution-processed ZTO-TFTs prepared at 350 °C using an alkoxide–chloride precursor combination showed a field-effect mobility of 4.17 cm2 V−1 s−1, whereas that prepared using a chloride-only solution showed a mobility of 0.98 cm2 V−1 s−1. Thermal analysis showed that the alkoxide–chloride precursor was decomposed well at a given annealing temperature and formed oxide with few residual impurities compared with chloride-only precursors.