The title compound, [Cd₂(SO₃)₂(C₁₈H₁₂N₆)₂]·8H₂O, is a dimer built up around a symmetry center, where the sulfite anion displays a so far unreported coordination mode in metal-organic complexes; the anion binds as a μ₂-sulfite-κ⁴O,O′:O′,O″ ligand to two symmetry-related seven-coordinate Cd^II cations, binding through its three O atoms by way of two chelate bites with an O atom in common, which acts as a bridge. The cation coordination is completed by a 2,4,6-tri-2-pyridyl-1,3,5-triazine ligand acting in its usual tridentate mode.