In the title compound, C17H15ClN2O2, the benzene rings form dihedral angles of 89.56 (5) and 5.87 (5)° with the mean plane of the pyrazoline ring (r.m.s. deviation = 0.084 Å). The dihedral angle between the two benzene rings is 87.57 (5)°. In the crystal, molecules are linked by O—HO and C—HO hydrogen bonds into a helical chain along the c axis. Between the chains weak C—HN and C—HO interactions are present. The crystal studied was an inversion twin with a domain ratio of 0.72 (4):0.28 (4).