In the novel title six-coordinate cadmium complex, [Cd(S₂O₃)(C₁₂H₈N₂)]_n, the anion binds to three different six-coordinate cationic centres through all four external atoms, an unprecedented coordination mode for thiosulfate metal-organic complexes. This connectivity leads to strongly linked dimers, connected to form interleaved double chains, which in turn interact through remarkably short π–π bonds between their phenanthroline groups.