In the title compound, {[Ca(3)Eu(2)(C(7)H(3)NO(4))(6)(H(2)O)(12)]·10.5H(2)O}(n), the Eu(III) ion is nine-coordinated by three tridentate pyridine-2,6-dicarboxyl-ate (PDA) ligands, forming a [Eu(PDA)(3)](3-) building block. The Ca(2+) ions adopt two types of coordination geometries. One Ca(2+) ion, lying on a twofold rotation axis, is eight-coordinated by four carboxyl-ate O atoms from four PDA ligands and four water mol-ecules, and the other two Ca(2+) ions, each lying on an inversion center, are six-coordinated by two carboxyl-ate O atoms from two PDA ligands and four water mol-ecules. The carboxyl-ate groups bridge the Eu(III) and Ca(2+) ions into a three-dimensional porous framework, with channels extending along [010] and [001] in which lattice water mol-ecules are located. Two of the lattice water mol-ecules are disordered over two sets of sites with equal occupancy and one water mol-ecule is 0.25-occupied. Numerous O-H⋯O hydrogen bonds involving the water mol-ecules and carboxyl-ate O atoms are present.