Different fluxes had been used in the preparation of AlN:Eu2+ blue phosphors by the carbothermal reduction method. The influence of these fluxes on the phase composition, crystallinity, particle size, and photoluminescence (PL) of the produced phosphors was investigated. X-ray diffraction and microstructure characterizations showed that both CaF2 and BaF2 were excellent nitridation promoters for the synthesis of AlN:Eu2+ phosphors, because pure and highly crystallized AlN was obtained with 3 wt% fluxes. The use of CaF2 flux resulted in phosphors which featured a very weak blue shift emission due to lattice distortion and lattice imperfection caused by the incorporation of Ca into the AlN host, according to the results of IR spectra, decay curves, and the changes in lattice parameters. In comparison with phosphors produced without the use of fluxes, the use of BaF2 flux resulted in phosphors with higher PL intensity by a factor of 2.4, which were produced at lower soaking temperature and shorter soaking time. Finally, a simple reaction mechanism for the nitridation process was also suggested.