In this paper, we prove that indium tin oxide (ITO) can be a material of choice for wavelength-selective thermal emitters that enable operation in ambient air. The wavelength-selective thermal emission is achieved by plasmonic ITO perfect absorbers (IPAs) composed of ITO – Al_2O_3 – ITO tri-layers where the top ITO layer is a hexagonal array of ITO disks. Simulated optical spectra of the IPAs reveal nearly perfect absorptivities (i.e. 0.99) at obvious resonances, which can be easily tuned just by changing the size of the ITO disks. The fabricated IPAs that followed the pre-designed simulation also exhibit excellented resonant absorptivities (i.e. 0.92), as well as good resonance tunability, which indicate the appreciable performance of IPAs. Furthermore, we show that IPAs are also feasible to serve as highly-efficient thermal emitters that can operate in ambient air without the need for strict vacuum or inert gas conditions, providing another platform for IR plasmonic devices.