The asymmetric unit of the title compound, (C(5)H(14)N(2))[SbCl(5)]·H(2)O, consists of an N-methyl-piperazinediium cation, a penta-chloridoanti-monate anion with the Sb(III) ion in a slightly distorted square-pyramidal coordination environment, and one solvent water mol-ecule. The crystal structure is stabilized by inter-molecular N-H⋯Cl, O-H⋯Cl and N-H⋯O hydrogen bonds.