Xylene is a flammable, toxic and harmful inert gas. Achieving highly selective detection of xylene gas is essential for protecting the environment and health, but is full of challenges. Herein, NiCo2O4 with multilayer hexagonal structure has been synthesized through a combination strategy of hydrothermal and annealing, and is applied to detect xylene gas. The effect of composition, surface area, crystallinity and porous degree on gas sensing performance has also been investigated. NiCo2O4 multilayer hexagonal structures annealed at 400 °C (NCO MHs-400) exhibit a better gas sensing selectivity toward xylene gas compared to NiCo2O4 multilayer hexagonal structures annealed at 500 °C and at 600 °C (NCO MHs-500 and NCO MHs-600), which predominantly originates from the catalytic oxidation of cobalt component to xylene in the as-prepared pure phase NiCo2O4. Furthermore, NCO MHs-400 presents a superior stability and reliability, well moisture resistance, and a detection limit of 1 ppm toward xylene at a working temperature of 170 °C.