In the title complex, {[Ho(C(2)O(4))(C(6)H(4)NO(3))(H(2)O)]·(H(2)O)}(n), the Ho(III) ion is coordinated by three O atoms from two 2-oxidopyridinium-3-carboxylate ligands, four O atoms from two oxalate ligands and one water mol-ecule in a distorted bicapped trigonal-prismatic geometry. The 2-oxidopyridin-ium-3-carboxylate and oxalate ligands link the Ho(III) ions into a layer in (100). These layers are further connected by inter-molecular O-H⋯O hydrogen bonds involving the coordinated water mol-ecules to assemble a three-dimensional supra-molecular network. The uncoordin-ated water mol-ecule is involved in N-H⋯O and O-H⋯O hydrogen bonds within the layer.