In the title complex, [PdCl₂(C₁₂H₂₂S₃)]·0.8CH₃CN, a potentially tridentate thio­ether ligand coordinates in a cis-bidentate manner to yield a square-planar environment for the Pd^II cation [mean deviation of the Pd from the Cl₂S₂ plane = 0.0406 (7) Å]. Each square-planar entity packs in an inverse face-to-face manner, giving pairs with plane-to-plane separations of 3.6225 (12) Å off-set by 1.1263 (19) Å, with a PdPd separation of 3.8551 (8) Å. A partial aceto­nitrile solvent mol­ecule is present. The occupancy of this mol­ecule was allowed to refine, and converged to 0.794 (10). The synthesis of the previously unreported 3,6,9-tri­thiabi­cyclo­[9.3.1]penta­decane ligand is also outlined.