Graphene oxide (GO) and graphene oxide-zinc oxide nanocomposites (GO-ZnO) were used as channel materials on SiO2/Si to fabricate thin-film transistors (TFT) with an aluminum source and drain. Pure GO-based TFT showed poor field-effect characteristics. However, GO-ZnO-nanocomposite-based TFT showed better field-effect performance because of the anchoring of ZnO nanostructures in the GO matrix, which causes a partial reduction in GO as is found from X-ray photoelectron spectroscopic data. The field-effect mobility of charge carriers at a drain voltage of 1 V was found to be 1.94 cm2/(V s). The transport of charge carriers in GO-ZnO was explained by a fluctuation-induced tunneling mechanism.