In the title coordination polymer, [Pb(C5H2N2O4)(H2O)](n), the Pb(II) atom is seven-coordinated by one N atom and five O atoms from four individual imidazole-4,5-dicarboxylate (HIDC2-) groups and one water molecule. It is interesting to note that the HIDC2- group serves as a bridging ligand to link the Pb(II) atoms into a three-dimensional microporous open-framework.