In the mol-ecule of the title compound, C(17)H(15)N(3)O(3)S·0.5H(2)O, the thia-diazole ring is oriented with respect to the two 2-methoxy-phenyl rings at dihedral angles of 3.70 (3) and 1.74 (2)°. An intra-molecular N-H⋯O hydrogen bond results in the formation of a planar six-membered ring, which is oriented with respect to the thia-diazole ring at a dihedral angle of 1.33 (3)°. Thus, all of the rings are nearly coplanar. In the crystal structure, inter-molecular O-H⋯N and C-H⋯O hydrogen bonds link the mol-ecules.