Oxygen vacancy engineering is an efficient strategy to improve the catalytic performance of nanomaterials. In this work, a highly active Fe-modified manganese oxide (Fe-MnOx) was synthesized and used for airborne ozone decomposition. The addition of Fe3+ during MnO2 synthesis led to higher specific surface area, greatly increased content of oxygen vacancies, evidenced by XPS, H-2-TPR analysis and lower oxygen vacancy formation energy (decreased by similar to 1.2 eV) based on the density functional theory calculations. The ozone conversion over Fe-MnOx kept 97% after 24 h reaction, while it over MnO2 slowed down to 85% under dry condition. Remarkably, under humid condition (RH = 60%), the ozone conversion over Fe-MnOx kept 73% after 6 h reaction, while ozone conversion over pure MnO2 decreased to 50% within 1 h under the conditions of 100 ppm inlet ozone concentration and weight space velocity of 660 L g(-1) h(-1). The intermediate peroxide species (O-2(2-)) formed on the surface oxygen vacancies of Fe-MnOx and MnO2 during ozone decomposition reaction were observed using in situ Raman spectroscopy. The concentration and depletion rate of O-2(2-) on the surface of Fe-MnOx was higher than that on MnO2, illustrating that O-2(2-) acted as the key species to boost the catalytic process. The content and dispersity of oxygen vacancies were identified to be mainly responsible for the performance difference. This provides a promising idea for designing novel nanomaterial catalyst for gaseous ozone decomposition.