In the bimetallic cyanide-bridged title complex, [Fe(0.98)HoRu(0.02)(CN)(6)(C(3)H(7)NO)(4)(H(2)O)(3)]·H(2)O, the Ho(III) ion is in a slightly distorted square-anti-prismatic arrangement formed by seven O atoms from four dimethyl-formamide (DMF) mol-ecules and three water mol-ecules, and one N atom from a bridging cyanide group connected with the Fe(III) atom which is octa-hedrally coordinated by six cyanide groups. In the crystal, mol-ecules are held together through O-H⋯N and O-H⋯O hydrogen-bonding inter-actions to form a three-dimensional framework. Elemental analysis of one of the precursors and the crystal shows that there is a slight contamination of Fe by Ru. The Fe site displays, therefore, small substitutional disorder with site-occupancy factors Fe/Ru = 0.98:0.02. The two methyl groups of two dimethyl-formamide ligands are positionally disordered with site-occupancy factors of 0.44 (3):0.56 (3) and 0.44 (3):0.56 (3).