The title compound, [Ce(C(3)H(9)OP)(4)(H(2)O)(4)]Cl(3).3H(2)O, contains eight-coordinate Ce atoms in an approximate dodecahedral arrangement, with Ce-O(P) = 2.372 (2)-2.423 (2) A and Ce-O(H(2)) = 2.518 (2)-2.630 (2) A.