Heterostructured semiconductor materials, combining the collective advantages of individuals and synergistic properties, have spurred great interest as a new paradigm toward detecting of volatile organic compounds recently. Direct use of NiS as a sensing material is impractical because the structure of NiS is unstable, exhibiting an undesirable sensing performance. Herein, we firstly report its incorporation into an ethanol gas sensor with a conventional n-type sensitive material of In2O3, and the gas sensing performance of the NiS@In2O3 nano-composites has been significantly enhanced. Nanofiber-like NiS and In2O3 were fabricated via a synergetic approach of electrospinning and calcination processes. The diameters of crystalline NiS and In2O3 are about 150 nm and 120 nm, respectively. Then, the NiS@In2O3 nanocomposites were prepared via re-calcination of as-prepared NiS and In2O3 nanofibers. The results show that the sensor based on NiS@In2O3 exhibits a detecting limit of as low as 5 ppm and a short response time of 8 s at the optimum temperature of 300 degrees C, which outstripped that (13 s) of pristine In2O3 and pure NiS sensors (21 s) for the detection of ethanol gas. The remarkable improvement of sensing performance can be attributed to the p-n heterojunction in multi-component phases of NiS and In2O3.