In this paper  ZnO/ZnS core/shell nanostructures are used to fabricate the gas sensor which can sense low concentration of acetone gas at room temperature. Due to its reducing properties, acetone gas releases electrons to the surface of the core/shell nanorods. Therefore a sharp increase in conductivity of the sensing material was observed when the sensor was exposed to the acetone gas. The fabricated sensor exhibited excellent sensitivity towards acetone gas at room temperature and is capable of detecting it to a minimum concentration of 10 ppm.