In the title compound, [Fe(C(5)H(3)N(2)O(4))(2)](n), each Fe atom lies on a centre of symmetry, in an octahedral coordination environment consisting of two chelate rings [Fe-N = 2.154 (3) A and Fe-O = 2.180 (3) A] and two carboxylate O atoms [Fe-O = 2.111 (2) A] from imidazole-4,5-dicarboxylate ligands. Extensive hydrogen-bonding interactions exist between layers constructed of Fe(4) squares, forming tunnels along the a axis with large voids.