In the title compound, C(13)H(16)N(10)O(2)S·C(5)H(9)NO·H(2)O, the entire 1-methylpyrrolidin-2-one (NMP) mol-ecule is disordered over two sites with occupancies of 0.488 (5) and 0.512 (5). The six-membered triazine ring and the two five-membered pyrazole and thiadia-zole rings, together with the diazene (-N=N-) linkage are almost coplanar (r.m.s. deviation for the non-H atoms = 0.0256 Å) with methyl groups from the tert-butyl substituent on the pyrazole ring located above and below the plane. Three intra-molecular N-H⋯N hydrogen bonds contribute to the planarity of the system. The O atom of the NMP mol-ecule is hydrogen bonded to an O-H group of water. In turn, the water mol-ecule is hydrogen bonded to the mono-azo skeleton through inter-molecular N-H⋯O and O-H⋯N hydrogen bonds. At both ends of the long mol-ecular axis of the main mol-ecule there are inter-molecular N-H⋯N hydrogen bonds, arranged in a head-to-tail fashion, between the N-H group of the triazine ring of one mol-ecule and the N atom of the thia-diazole ring of a neighboring mol-ecule. These form a polymeric chain along [110] or [10]. The main mol-ecules are stacked alternately along the b axis, which effectively cancels their dipole moments. In addition, pairs of alternate molecules are dimerized via inter-molecular hydrogen bonds involving the solvent mol-ecules.