Multi-Arc Ion Plating (MAIP) technology was used to deposit yttrium oxide (Y2O3) ceramic thin fflms on Al2O3 ceramics and silicon wafers. The effects of varying the O-to-Ar gas ffow ratio (Rc: 0.5, 1.0, 1.5, 2.0) and the annealing conditions on the phase composition, microstructure, mechanical properties, and tribological performance of the Y2O3 fflms were assessed. The fflms deposited at Rc values of 1.0 and 1.5 consisted of a single cubic phase structure. In contrast, fflms deposited at Rc values of 0.5 and 2.0 contained a small monoclinic phase and the cubic phase structure. The fflm deposited at an Rc value of 1.0 (oxygen ffow rate of 200 sccm) exhibited a dense microstructure, the best mechanical properties (hardness of 14.2 ± 0.191 GPa), and the lowest friction coefffcient (0.142 ± 0.003). Furthermore, the colour of the fflm changed from grey-black to white after annealing at 800 ◦C for 6 h. The oxygen vacancy of the thin fflm increased, with improving crystallinity, decreasing hardness and elastic modulus, and increasing grain size, friction coefffcient and wear rate. The fflm exhibited the best tribological properties at 25 ◦C.