The Co-II atom in bis(5-aminotetrazole-1-acetato)tetraaquacobalt(II), [Co(C3H4N5O2)(2)(H2O)(4)], (I), is octahedrally coordinated by six O atoms from two 5-aminotetrazole-1-acetate (atza) ligands and four water molecules. The molecule has a crystallographic centre of symmetry located at the Co-II atom. The molecules of (I) are interlinked by hydrogen-bond interactions, forming a two-dimensional supramolecular network structure in the ac plane. The Cd-II atom in catenapoly[[cadmium(II)]-bis(mu-5-aminotetrazole-1-acetato], [Cd(C3H4N5O2)(2)](n), (II), lies on a twofold axis and is coordinated by two N atoms and four O atoms from four atza ligands to form a distorted octahedral coordination environment. The Cd-II centres are connected through tridentate atza bridging ligands to form a two-dimensional layered structure extending along the ab plane, which is further linked into a three-dimensional structure through hydrogen-bond interactions.