In the title compound, C14H14ClN3O2, the morpholine ring adopts a chair conformation, with the exocyclic N-C bond in an equatorial orientation. The 1,6-dihydropyridazine ring is essentially planar, with a maximum deviation of 0.014 (1) angstrom, and forms a dihedral angle of 40.16 (7)degrees with the plane of the benzene ring. In the crystal, pairs of centrosymmetrically related molecules are linked into dimers via N-H center dot center dot center dot O hydrogen bonds, forming R2 2 (8) ring motifs. The dimers are connected via C-H center dot center dot center dot O and C-H center dot center dot center dot Cl hydrogen bonds, forming a three-dimensional network. Aromatic pi-pi stacking interactions [centroid-centroid distance = 3.6665 (9) angstrom] are also observed. Semi-empirical molecular orbital calculations were carried out using the AM1 method. The calculated dihedral angles between the pyridizine and benzene rings and between the pyridizine and morpholine (all atoms) rings are 34.49 and 76.96 degrees, respectively.The corresponding values obtained from the X-ray structure determination are 40.16 (7) and 12.97 (9)degrees, respectively. The morpholine ring of the title compound in the calculated gas-phase seems to have a quite different orientation compared to that indicated by the X-ray structure determination.