In the title compound, C(18)H(21)N(3)O(2)S·0.5H(2)O, the benzene ring makes dihedral angles of 88.59 (6) and 40.74 (8)° with the pyridine ring and the amide group, respectively. The water O atom lies on a twofold axis. In the crystal, the organic mol-ecules and the water mol-ecules are linked via O-H⋯O hydrogen bonds, while the organic mol-ecules are connected to each other via N-H⋯O hydrogen bonds, forming a three-dimensional network.