The porous flake-like Co₃O₄and Co₃O₄/graphene hybrids with different graphene contents were prepared through a facile two-step method. The field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) characterizations proved the tight adherence of graphene sheets to the surface of porous Co₃O₄slices. Gas sensors based on the as-synthesized products were then fabricated to explore their potential applications. The results indicated that the optimal hybrid exhibited a response of 26.8% to 5 ppm of NO₂at room temperature (RT), which was 2.27 times higher than that of undoped Co₃O₄(100℃). The hybrid sensor also showed fast response, excellent selectivity, long-term stability and extremely low detection limit toward NO₂at RT. The significantly enhanced sensing properties to NO₂could be attributed to larger specific surface area, more chemisorbed oxygen species and the coupling effect between Co₃O₄and graphene in the hybrid. As we all know, as a typical p-type semiconductor, the gas-sensing properties of Co₃O₄toward oxidizing gases including NO₂was rarely reported. We believe that our work could pave the way for the future design of Co₃O₄-based gas sensors for oxidizing gases detection at low or even room temperature.