The asymmetric unit of the title compound, C(22)H(15)Cl(4)NO(2)·0.5H(2)O, consists of a (3E,5E)-1-acryloyl-3,5-bis-(2,4-dichloro-benzyl-idene)piperidin-4-one mol-ecule and a half-mol-ecule of water (the O atom of the water mol-ecule lies on a twofold axis). The piperidin-4-one ring adopts an envelope conformation. The dihedral angle between the two terminal benzene rings is 8.84 (11)°. In the crystal, mol-ecules are connected by C-H⋯O hydrogen bonds forming supra-molecular chains along the c axis. Furthermore, adjacent chains are inter-connected by the water mol-ecules via O-H⋯O hydrogen bonds.