The title compound, [Cu₂Cl₄(C₁₄H₁₄N₂)₂], is a new polymorph of a previously reported compound [Dehghanpour et al. (2011 ▶). Acta Cryst. E67, m1296]. The current polymorph was obtained from an acetonitrile solution of the title compound. Like the first polymorph, it is monoclinic (space group P2₁/c). The unique Cu(II) ion in the title centrosymmetric dinuclear complex is in a distorted trigonal-bipyramidal coordination environment formed by the bis--chelating N-heterocyclic ligand, two bridging Cl ligands and one terminal Cl ligand. In the crystal, weak C-H⋯Cl hydrogen bonds are observed in addition to π-π stacking inter-actions, with a centroid-centroid distance of 3.6597 (18) Å.