Two-dimensional (2D) MoS₂/MoO₃ nanosheets have attracted significant attention for room-temperatureNO₂ gas sensing owing to their large surface areas and tunable electronic properties. In this work, pristine and Co-/Ni-doped MoS₂/MoO₃ nanosheets were synthesized at 240 °C via a hydrothermal method. Structural and morphological characterizations confirmed the formation of a semiconducting 2H phase in pristine MoS₂/MoO₃, while Co and Ni doping induced slight lattice distortions. Gas-sensing measurements showed that at room temperature, pristine MoS₂/MoO₃ exhibited a response of ~28% at 1 ppm, which increased to ~46% at 50 ppm of NO₂ gas concentrations. The response improved further when the operating temperature was raised to 55 °C. The doping-induced lattice strain promoted NO₂ adsorption and led to slower recovery compared with the pristine sample. Selectivity tests indicated a stronger response to NO₂ than to ammonia (NH₃), acetone (C₃H₆O), ethylene (C₂H₄), and methane (CH₄) under identical conditions. Density functional theory (DFT) calculations revealed that doping modified the Mo-S bond lengths and electronic structure, thereby affecting the adsorption and charge-transfer behavior, consistent with our experimental observations. These findings provide insights into how subtle structural modifications influence the gas-sensing performance, guiding the design of high-performance MoS₂-based sensors and other transition-metal-sulfide systems.