In this paper, a series of Er(3+)-doped Y2O3 samples are systematically investigated, focusing on the effect of the doping concentration on the emission lifetime and spectrum under both 488 nm and 980 nm excitations. Decay times of the (4)S3/2 and (4)F9/2 emitting states under 488 nm and 980 nm excitations are found to be different and concentration dependent. We explain these variations in terms of the changes in the up-conversion routes caused by the predominance of energy exchanges that involve the lowest lying excited states.