In the title compound, C 19H 18N 4O 2, the 1,8-naphthyridine ring system is essentially planar [r.m.s. deviation = 0.011 (3) Å]. The dihedral angle between the naphthyridine ring system and the phenyl ring is 28.95 (7)°. The carbohydrazide H atom is involved in an intramolecular N—H⋯O hydrogen bond, forming a six-membered hydrogen-bonded ring. In the crystal, the molecules arrange themselves into centrosymmetric dimers by means of intermolecular C—H⋯O hydrogen bonds.