The title compound, C19H21N3O, has a supramolecular structure of hydrogen bonding comprising N—H⋯O bonds which form a series of anti-parallel C(8) chains linked together by N—H⋯N R22(8) base-paired motifs which together form corrugated sheets containing R66(34) rings. This is one of a series of four substituted 3,7,7-tri­methyl-4,7,8,9-tetra­hydro-2H-pyrazolo­[3,4-b]­quinolin-5(6H)-one compounds which all have identical supramolecular structures.