We present a detailed study on post synthesis annealing effects on luminescence as well as electronic and structural properties of pure and Terbium doped (5 wt%) CePO₄ nanowires (NWs) prepared using green synthesis chemical route. The formation of nanowire was confirmed from transmission electron microscopy and small angle X-ray scattering measurements, revealing elongated nanowire shape with monoclinic crystal structure in agreement with X-ray diffraction observations. Photoelectron spectroscopy data analysis showed that samples annealed under air consist of only Ce⁴⁺ oxidation state, while those annealed under N₂ environment showed the presence of mixed Ce⁴⁺ and Ce³⁺ oxidation states. However, this Ce⁴⁺ oxidation state has not propagated inside the bulk of NWs as seen from X-ray absorption spectra around Ce L_III absorption edge. The photoluminescence measurements revealed significant differences between the samples annealed in air and N₂ flow respectively. Post synthesis annealing under N₂ flow helped to suppress the contribution of Ce⁴⁺ oxidation state in photoluminescence. The overall results are beneficial from the luminescent device point of view and form a basis for advance studies.