The X-ray diffraction study of Ba[Ni(Cdta)] · 10H2O is performed (R1 = 0.0441 for 5136 observed reflections). The crystals are triclinic, a = 8.833(2) A, b = 9.025(2) A, c = 16.922(3) A, α = 80.56(3)°, β = 82.77(3)°, γ = 76.98(3)°, Z = 2, and space group \(P\bar 1\). The crystal is built of the [Ni(Cdta)]2− anionic complexes, the [Ba(H2O)6]2+ hydrated cations, and crystallization water molecules. The distorted octahedral coordination of the Ni atom includes two N and four O atoms of the Cdta4− ligand (mean Ni-N, Ni-OG, and Ni-OR re 2.080, 2.082, and 2.036 A, respectively). The irregular nine-fold coordination of the Ba atom consists of six O atoms of water molecules and three O(Cdta) atoms from three anionic complexes (Ba—O, 2.715–3.090 A). With consideration for the bonds with three Ba atoms, the Cdta4− ligand is octadentate (2N + 6O) and fulfills the pentadentate μ4-bridging function. The structural units are linked through an extended network of hydrogen bonds.