Abstract: ZnSnO₃ nanocubes (ZSNCs) with various Pt concentrations (i.e., 1at%, 2at%, and 5at%) were synthesized by a simple one-pot hydrothermal method. The microstructures of pure and Pt-doped ZSNCs were characterized by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. Results showed that the pure ZSNCs have a perovskite structure with a side length of approximately 600 nm; this length was reduced to 400 nm after Pt doping. Following doping, PtO_x (PtO and PtO₂) nanoparticles with a diameter of approximately 5 nm were uniformly coated on the surface of the ZSNCs. Systematic investigation of the gas-sensing abilities of the nanocubes showed that the Pt-doped ZSNCs have excellent sensing properties toward nitrogen dioxide (NO₂) gas in the operating temperature range of 75–175°C. Among the sensors prepared, that based on 1at% Pt-doped ZSNCs exhibited the best response of 16.0 toward 500 ppb NO₂ at 125°C; this response is over 11 times higher compared with that of pure ZSNCs. The enhanced NO₂ sensing mechanism of the Pt-doped ZSNCs may be attributed to the synergistic effects of catalytic activity and chemical sensitization by Pt doping.