Dual-gated (DG) thin-film transistors (TFTs) with an amorphous InGaZnO (IGZO) channel are fabricated using a poly(4-vinyl phenol) polymer as a dielectric layer. Compared to single-gated (SG) devices, DG devices showed much stronger gate controllability and greatly enhanced device performance over conventional SG TFTs. Although all devices exhibited a positive V-th shift under positive bias stress, the highly stable V-th shift of 0.17 V was observed for the IGZO TFT with DG structure. It is demonstrated that DG operation is an appropriate gate configuration to produce high-performance TFTs, which is applicable to low-power devices.