In the title compound, {[Fe(CHO(2))(2)(C(10)H(8)N(2))(H(2)O)]·4H(2)O}(n), the Fe(II) ion is coordinated by two 4,4'-bipyridyl (4,4'-bpy) ligands, three formate ligands and one water molecule. The slightly distorted octahedral FeN(2)O(4) coordination results from the N atoms of two bridging 4,4'-bpy ligands, the O atoms of two bridging HCOO(-) anions of anti-anti mode, all in trans positions around the metal centre, and the O atoms of one terminal HCOO(-) anion and of one water molecule. The bridging formate ligands link the metal ions into chains that are further connected via 4,4'-bpy ligands into a framework structure. The three-dimensional structure is stabilized by extensive O-H⋯O hydrogen bonding. The crystals were twinned containing a 0.84:0.16 racemate.