The title compound, C(21)H(16)NP, is a known P-N chelator and various crystal structures of its metal complexes have been reported. However, no crystallographic evidence of the free ligand has been given to date. The phenyl rings are almost orthogonal to one another [dihedral angle = 88.9 (1)°], and they are twisted from the mean plane of the quinoline by 80.5 (1) and 76.3 (1)°.