A new H-bonded (H2O)38 water cluster was identified in a mixed-valent cerium dipicolinate complex [CeIV(dipic)3CeIII(H2O)8][CeIV(dipic)3CeIII(H2O) 7CeIV(dipic)3] · 20H2O (dipicH2=dipicolinic acid). Such a large cluster built around an inversion centre and occupying 20% of the unit cell volume is supported by the bulky acceptor rich complex ions in the crystal lattice. The compound crystallises in the triclinic crystal system with space group P1̄ and unit cell parameters; a=16.5285(9) Å, b=17.1905(10) Å, c=19.5220(11) Å, =76.0440(10)°, β=79.0180(10)°, γ=65.6370(10)Å, V=4877.7(5) Å3.