Here, we have demonstrated that carbohydrate ligand polycations are pH-dependently dissociated from DNA polyion complexes. In response to pH, DNA ternary complexes have dissociated the ligand polycations, resulting in DNA binary complexes. Namely, the ternary complexes of DNA, a poly(L-histidine) modified with aminoethyl groups, PLH-NH2, and a poly(L-lysine) conjugated with lactose molecules, PLL-Lac, at pH 7.5 have dissociated the PLL-Lac polycations by the protonation of imidazole groups of PLH-NH2 at pH 6.0. The pH-dependent dissociation of the ligand polycations from DNA polyion complexes at endosomal pH is expected to offer unique design for DNA delivery systems.