Zinc(II) formaldehyde sulfoxylate, [Zn(CH3O3S)2], a widely marketed additive in the polymer and textile industry (under the registered trademarks Decroline, Decolin and Safolin, CAS 24887‐06‐7), possesses, in the solid state, a polymeric framework, with the Zn atoms octahedrally coordinated by six O atoms of four different hydroxymethanesulfinate groups. The latter are found to coordinate through all their O atoms, including the hydroxy ones, and possess a chelating nature. By contrast, in the structure of the only other commercially available salt of this ligand (dihydrated sodium formaldehyde sulfoxylate), the organic residue, being involved in an extensive network of hydrogen‐bond contacts, is fully stretched and bridges two NaI ions through a single O atom.