The title complex, [CaZn(C3H2O4)2(H2O)4]n, is a two-dimensional polymer and consists of CaO8 and ZnO6 polyhedra linked together by malonate ligands. The Ca(II) cation, lying on a twofold axis, is coordinated by two water molecules and six malonate O atoms. The Zn(II) cation, which lies on an inversion center in an octahedral environment, is coordinated by four malonate O atoms in an equatorial arrangement and two water molecules in axial positions. The Zn-O and Ca-O bond lengths are in the ranges 2.0445 (12)-2.1346 (16) and 2.3831 (13)-2.6630 (13) angstroms, respectively. The structure comprises alternating layers along the [101] plane, the shortest Zn...Zn distance being 6.8172 (8) angstroms. The whole three-dimensional structure is maintained and stabilized by the presence of hydrogen bonds.