While plastic has been regarded as a useful and cost-effective material, there is growing global concern about its disposal. Chemical recycling presents a promising solution to this issue. This study explores the utilization of vanadium oxide as a redox catalyst to effectively decompose polystyrene into industrially useful CO. By heating polystyrene with V2O5 under an inert gas atmosphere, CO was successfully produced accompanied with CO2 as the primary by-product. Adding 5 wt% iron to V2O5 improved the selectivity of CO production without compromising gas yield. X-ray diffraction analysis indicated that V2O5 acted as an oxygen source and turned into V2O4 and V6O13 after the reaction. This process enables polymer reformation at lower temperatures than conventional methods, making it an energy-efficient chemical recycling strategy. Additionally, V2O4 and V6O13 generated during the process were easily oxidized to V2O5 through heating under atmospheric conditions. As both polymer reformation and oxidation are exothermic reactions, the proposed reaction scheme can be used as a thermally efficient chemical recycling process.