CeO₂ is a well-suited support due to its higher oxygen storage capacity and reversible redox ability, which is associated with the oxygen activation. Herein we report the effective oxygen activation in CeO₂ by gallium incorporation, varying the Ga/Ce molar ratios from 0.25 to 0.75. Structural results and operando spectroscopies under reaction conditions revealed that gallium incorporation improves the oxygen activation in CeO₂, being more effective at low gallium content (Ga/Ce of 0.25). Atomic-scale computations demonstrated that the 0.25 Ga/Ce molar ratio generates Ga atomic-size channels that allow an easy way for oxygen diffusion from bulk to the surface. Ga incorporates into the subsurface Ce layer causing a collective effect: weakening the surface Ce-O bonds, boosting the surface oxygen activation, then enhancing the CO oxidation ability. Once this happens, it leaves behind O-vacancies, which may occupy either bulk oxygen from the CeO₂ or further renovation of oxygen atoms from the environment.