The short-range order of a series of sodium-iron phosphate glasses has been studied through X-ray diffraction with the purpose of investigating the structural role of iron ions in these glasses. Fe-O bond lengths and coordination numbers were obtained by simulating the difference radial curves calculated by subtracting the radial distribution function of the proper sodium phosphate glass from those of sodium-iron phosphate glasses. Good fits were obtained by considering the occurrence of about 10% of Fe2+ and two distinct sites for Fe3+; octahedral coordination for all iron ions was demonstrated The difference radial curves show clearly that well-defined structural arrangements extending to medium-range distances form in all the examined cases around iron, which modifies the properties of glasses, by strengthening the cross-bonding of the phosphate chains.