•Up-to-date evaluation of graphene-based gas sensors.•Hybrids of graphene with noble metals, metal oxides, and conducting polymers.•Systematic comparison of gas-sensing principles graphene-based hybrids.•Systematic comparison of gas-sensing properties of graphene-based hybrids.•Presentation of future outlook for graphene-based hybrid gas sensors. Gas sensors can detect combustible, explosive and toxic gases, and have been widely used in safety monitoring and process control in residential buildings, industries and mines. Recently, graphene-based hybrids were widely investigated as chemiresistive gas sensors with high sensitivity and selectivity. This systematic review is therefore timely and necessary to evaluate the success of graphene-based hybrids in gas detection and to identify their challenges. We review the sensing principles and the synthesis process of the graphene-based hybrids with noble metals, metal oxides and conducting polymers to achieve better understanding and design of novel gas sensors. Our review will assist researchers to understand the evolution and the challenges of graphene-based hybrids, and create interest in development of gas-sensing techniques.