In the title compound, [Mn(2)(C(2)O(4))(C(5)H(3)N(2)O(2))(2)(H(2)O)(2)](n), the Mn(II) atom exhibits a distorted octa-hedral coordination geometry, with the centrosymmetric oxalate anion and the monoanionic pyrimidine-2-carboxyl-ate ligands generating a two-dimensional honeycomb network with a (6,3)-topology.