Two polymorphs of the title compound, C19H16N2O3, were obtained from ethanolic (polymorph I) and methanolic solutions (polymorph II), respectively. Both polymorphs crystallize in the monoclinic system with four formula units per cell and a complete molecule in the asymmetric unit. The main difference between the molecules of (I) and (II) is the reversed position of the hydroxy group of the carboxylic function. All other conformational features are found to be similar in the two molecules. The different orientation of the OH group results in different hydrogen-bonding schemes in the crystal structures of (I) and (II). Whereas in (I) intermolecular O-H center dot center dot center dot O hydrogen bonds with the pyridazinone carbonyl O atom as acceptor generate chains with a C(7) motif extending parallel to the b-axis direction, in the crystal of (II) pairs of inversion-related O-H center dot center dot center dot O hydrogen bonds with an R-2(2)(8) ring motif between two carboxylic functions are found. The intermolecular interactions in both crystal structures were analysed using Hirshfeld surface analysis and two-dimensional fingerprint plots.