Effective control of gas-phase pollutants (volatile organic compounds (VOCs) and CO) is critical to human health and the ecological environment. Catalytic oxidation is one of the most promising technologies for achieving efficient volatile organic compounds and CO emission control. The sub-nano cluster catalyst can not only provide catalytic sites with multiple metal atoms, but also maintain full utilization efficiency. Almost all metal atoms in highly dispersed clusters can be used for adsorption and conversion of reactants. Recently, various types of sub-nano clusters, including sub-nano cluster oxides, have been developed and demonstrated excellent performance in low-temperature gas-phase pollutants combustion. In this mini review, we systematically summarize the structure, physicochemical properties, characterization, and applications of sub-nano cluster catalysts in catalytic oxidation of CO, methane, propane, propylene, toluene and its derivatives, formaldehyde and chlorinated volatile organic compounds. Finally, we have analyzed and discussed the problems and challenges faced by sub-nano cluster catalysts in both basic research and practical applications, providing a scientific basis for the design, synthesis, and application of efficient heterogeneous catalysts for CO and VOCs oxidation.