In the title compound, C(20)H(19)N(3)O, the dihedral angles formed by the pyrazolone ring with the two phenyl rings are 64.27 (6) and 17.00 (6)°. The mol-ecular structure is stabilized by intra-molecular N-H⋯O and C-H⋯O hydrogen bonds. In the crystal, the mol-ecules are linked into chains along the b axis by inter-molecular C-H⋯O hydrogen bonds.