The interaction of gallium and palladium with 2 nm CeO2(111) layers grown on Cu(111) was studied by core level photoelectron spectroscopy and resonant valence band spectroscopy. Palladium alone interacted weakly with ceria layers. Gallium deposited on cerium dioxide formed a mixed Ga2O3–Ce2O3 oxide of 1:1 stoichiometry (cerium gallate CeGaO3), with both metals in the M3+ oxidation state. Increasing Ga coverages led to the formation of lower oxidation states, i.e., Ga1+ in Ga2O oxide and metallic Ga0. Palladium deposited onto this complex system interacted with gallium leading to a breakage of Ga–ceria bonds, a decrease of the oxidation state of gallium, and formation of a Ga–Pd intermetallic alloy in which all components (CeO2, CeGaO3, Ga2O, Ga–Pd, and Pd) are in equilibrium.