The title compound, [Hg(C(4)H(4)N(2)S)(C(4)H(3)N(2)S)](2)[HgBr(4)], consists of [Hg(pymt)(pymtH)](+) complex cations (pymtH is pyrimidine-2-thione) lying across twofold rotation axes in space group Fddd, with linearly coordinated mercury at an Hg-S distance of 2.357 (3) A, and [HgBr(4)](2-) anions lying at sites of 222 symmetry. The Hg atom is additionally coordinated by two N and two Br atoms, forming a 2+4 effective coordination sphere. The protonated ligand is connected via N-H.N hydrogen bonds to the neighbouring unprotonated ligand, thus forming infinite chains of cations.