In the structure of the title complex, [Cu(C8H4O4)(C12H8N2)(H2O)]·C3H7NO, the CuII ion is pentacoordinated in a distorted square-pyramidal geometry by two O atoms of a 3-formyl-2-oxidobenzoate dianion and two N atoms of a 1,10-phenanthroline ligand occupying the basal plane and a water O atom located at the apical site. The structure displays O—H...O hydrogen bonding and intermolecular π–π stacking interactions between 1,10-phenantroline ligands [interplanar distance of 3.448 (5) Å].