Anion-controlled circular dichroism (CD) spectral changes in Hg2+ complexes with a chiral bidentate ligand are reported. Although the Hg(CF3SO3)(2) and Hg(CF3CO2)(2) complexes with (R)-(-)-1-(naphthalen-1-yl)-N,N-bis(pyridin-4-ylmethyl)ethanamine, (R)-(-)-1, show significant CD spectral changes, no CD spectral changes were observed in the HgCl2, HgBr2, Hg(CN)(2), or Hg(CH3CO2)(2) complexes. X-ray analysis indicates that both the (R)-(-)-1-Hg(CF3SO3)(2) and (R)-(-)-1-HgCl2 complexes form a coordination polymer and a discrete 2:3 [=(R)-(-)-1/H8Cl2] complex with a figure-eight structure. X-ray crystallography revealed that (i) the Hg Hg distances bridged by anions vary depending on the anions used and (ii) a coordination polymer cannot be formed when the Hg Hg distances are too short. Therefore, the formation of a coordination polymer is required to give the observed significant CD spectral changes.