In the title complex, [Ni(C6H9N2O3S)2(H2O)2]·2H2O, the NiII atom lies on an inversion center and is chelated by N and O atoms of two symmetry-equivalent imidazolesulfonate ligands in the basal plane, and two water O atoms in axial positions in an overall octahedral configuration. The crystal structure displays O—H⋯O and N—H⋯O hydrogen bonds, which connect the components into an extended three-dimensional network.