Structures of (FeO)x(P2O5)1−x glasses with 0.2 ≤ x ≤ 0.5 are studied by x-ray diffraction using high energy photons from a synchrotron. Scattering intensities are obtained up to Qmax of 250 nm−1. P-O, Fe-O and O-O first-neighbour peaks are well resolved in the pair distribution functions. Constant P-O coordination numbers of 4.0 ± 0.1 with distances of 0.155 ± 0.001 nm are found as expected for PO4 tetrahedra. Mean Fe(II)-O coordination numbers of ~5 with distances of ~0.210 nm are extracted from fitting the Fe-O peaks where the oxygen coordination number of the minor fraction of 5-18% Fe(III) was set to six with Fe-O distances of 0.200 nm. The existence of FeO5 or strongly distorted FeO6 polyhedra instead of densely packed FeO6 octahedra for the Fe(II) sites is attributed to the mixed oxide effect. Fe3+ cations in rigid FeO6 octahedra hinder the Fe2+ cations in forming well defined octahedral environments.