In the structure of the novel zinc complex catena-poly[[diaqua(4-hydroxybenzohydrazide)zinc(II)]-μ-sulfato], [Zn(SO4)(C7H8N2O2)(H2O)2]n, the complex cations are linked by sulfate counter-ions into helical polymeric chains extending along the b axis. Each helix is stabilized by six intrachain hydrogen bonds involving stronger O-H...O (1.83-2.06 Å) and weaker N-H...O (2.20-2.49 Å) interactions. The Zn(II) atom displays a distorted octahedral geometry formed by the 4-hydroxybenzohydrazide ligand, two water molecules and two SO4(2-) ions, which is very similar to the metal-atom environment in a previously reported Co(II) complex [Zasłona, Drożdżewski & Kubiak (2010). J. Mol. Struct. 982, 1-8], especially the Zn-O and Zn-N bond lengths of 2.0453 (12)-2.1602 (9) and 2.1118 (12) Å, respectively.