The use of the anionic dicopper(II) complex, [Cu^II(mpba)₂]⁴⁻ [mpba = N,N′-1,3-phenylenebis(oxamate)], as tetrakis(bidentate) metalloligand toward Mn^II ions in the presence of oxalate and the chiral (S)-trimethyl-(1-phenylethyl)ammonium cation affords the first example of a mixed oxalato/oxamato-based chiral 3D metal–organic polymer.