A　homochiral　helical　three-dimensional　coordination　polymer,　poly[[(μ2-acetato-κ3　O,O＇:O)(hydroxido-κO)(μ4-5-nicotinamido-1H-1,2,3,4-tetrazol-1-ido-κ5　N1,O:N2:N4:N5)(μ3-5-nicotinamido-1H-1,2,3,4-tetrazol-1-ido-κ4　N1,O:N2:N4:N5)dicadmium(II)]　0.75-hydrate],　{[Cd2(C7H5N6O)2(CH3COO)(OH)]·0.75H2O}　n　,　was　synthesized　by　the　reaction　of　cadmium　acetate,　N-(1H-tetrazol-5-yl)isonicotinamide　(H-NTIA),　ethanol　and　H2O　under　hydrothermal　conditions.　The　asymmetric　unit　contains　two　crystallographically　independent　CdII　cations,　two　deprotonated　5-nicotinamido-1H-1,2,3,4-tetrazol-1-ide　(NTIA-)　ligands,　one　acetate　anion,　one　hydroxide　anion　and　three　independent　partially　occupied　water　sites.　The　two　CdII　cations,　with　six-coordinated　octahedral　and　seven-coordinated　pentagonal　bipyramidal　geometries　are　located　on　general　sites.　The　tetrazole　group　of　one　symmetry-independent　NTIA-　ligand　links　one　of　the　independent　CdII　cations　into　61　helical　chains,　while　the　other　NTIA-　ligand　links　the　other　independent　CdII　cations　into　similar　but　unequal　61　helical　chains.　These　chains,　with　a　pitch　of　24.937(5)Å,　intertwine　into　a　double-stranded　helix.　Each　of　the　double-stranded　61　helices　is　further　connected　to　six　adjacent　helical　chains　through　an　acetate　μ2-O　atom　and　the　tetrazole　group　of　the　NTIA-　ligand　into　a　three-dimensional　framework.　The　helical　channel　is　occupied　by　the　isonicotinamide　groups　of　NTIA-　ligands　and　two　helices　are　connected　to　each　other　through　the　pyridine　N　and　carbonyl　O　atoms　of　isonicotinamide　groups.　In　addition,　N-H⋯O　and　O-H⋯N　hydrogen　bonds　exist　in　the　complex.　©　2015　International　Union　of　Crystallography.