A high-performance hydrogen sulfide (H2S) gas sensor based on copper oxide (CuO)/molybdenum disulfide (MoS2) nanohybrid was demonstrated in this paper. A facile one-step hydrohermal method was used to synthesize CuO nanorods and MoS2 nanosheets. The CuO/MoS2 film sensor was developed on a substrate through layer-by-layer (LbL) self-assembly technique. The morphology, microstructure, and elementary composition of the as-prepared samples were inspected by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscope (TEM). The gas-sensing performance of the CuO/MoS2 sensor was fully measured at room temperature of 25 °C. As the experimental results shown, the CuO/MoS2 sensor achieved high response, short response/recovery time, outstanding repeatability, excellent selectivity, and steady long-term stability for H2S detection. The enhanced H2S sensing performance of the CuO/MoS2 sensor was given the credit to the synergistic effect of binary nanostructure and modulation of charge transfer by the heterojunction.