In the title compound, C(17)H(21)N(3)O(3)S, the dihedral angle between the aromatic ring planes is 84.2 (2)°. The pendant ethyl groups of the -N(C(2)H(5))(2) group are disordered over two sets of positions in a 0.84 (2):0.16 (2) ratio. The mol-ecular conformation is stabilized by an intra-molecular O-H⋯N hydrogen bond, and inter-molecular N-H⋯O bonds lead to [010] chains in the crystal structure.