The asymmetric unit of the title compound, [Zn(C(12)H(12)N(2))(H(2)O)(4)]SO(4), consists of a Zn(II) complex cation, a sulfate anion and four mol-ecules of water coordinated to the Zn(II) atom. The Zn(II) complex cation, with approximate twofold symmetry, displays a slightly distorted octa-hedral geometry around the Zn(II) atom, which is coordinated by two N atoms from a 5,5'-dimethyl-2,2'-bipyridine ligand and by the O atoms of four water mol-ecules. In the crystal, O-H⋯O hydrogen bonds help to establish the packing.