In the title compound, C22H22N2O2, the two central fused pyridazine rings have screw-boat conformations and the dihedral angle between their mean planes is 36.22 (8)°. The mean plane of the cinnoline ring system makes a dihedral angle of 46.56 (5)° with the mean plane of the phthalazine ring to which it is fused. In the crystal, molecules are linked via C—H...O hydrogen bonds, forming chains along the b axis. The chains are reinforced by C—H...π interactions.