Detecting methane (CH4) with good selectivity is one of the most important safety precautions to prevent catastrophic incidents in the current industrial environment. Detection of small molecular size, inert and nonpolar characteristic gases at trace levels using chemiresistive technique at room temperature is still challenging because of weak adsorption between gas and sensing material. Therefore, we fabricated a single-phase high entropy oxide based chemiresistor and tested it towards the various gases and several hydrocarbons at room temperature, but the sensor displayed a higher selectivity to CH4 gas than other gases. Further, the sensor characteristics revealed a significant response to CH4 gas, good response and recovery time, good long-term stability, and an experimental detection limit of 25 ppm. Besides, the as-fabricated sensor is low-cost, small in size and consumes 50 nW power, much lower than the other commercialized light-based sensors. As proof of concept, the fabricated sensor was utilized to measure CH4 gas in a real-time atmosphere. The sensor reflected response characteristics similar to the controlled environment and recovered without carrier gas. This facile approach sheds light on the rational design of high-entropy oxides, paving the way for mass production and commercialization of ultra-trace gas detection sensors with superior sensing capability. © 2022 Elsevier B.V.