The mixed electronic ionic conducting materials (Ba0.5Sr0.5) (Co0.8Fe0.2)1 хNbхO3 d with partial Nb substitution (x: 0.05, 0.10, 0.15, 0.20) for B cations (Co/Fe), synthesized using a solid state reaction method, have been studied by near edge X-ray absorption fine structure (NEXAFS). Co L2,3- absorption spectra of (Ba0.5Sr0.5) (Co0.8Fe0.2)1 хNbхO3 d (BSCFN) powders were analyzed with the purpose to understand the influence of the Nb substitution on the atomic electronic structure of BSCFN. The joint analysis of the Co L2,3- absorption spectra reveals the presence of mixed oxidation states Co2þ/Co3þ in all the studied BSCFN structures. It was established that the proportion of oxidation states Co2þ/Co3þ and the corresponding coordinations of Co atoms depend on the content of Nb. In the 10% Nb substituted BSCF sample Co atoms mostly occur in the Co2þ oxidation state and are preferentially characterized by an octahedral coordination site. In all other structures Co atoms are rather characterized by Co2þ/Co3þ oxidation states and occupy both octahedrally and tetrahedrally coordinated sites.