The molecular structure of the title compound, C21H18O4, consists of a 3,4-dimethoxyphenyl ring and a naphthalene ring system linked via a prop-2-en-1-one spacer. The molecule is almost planar, with a dihedral angle between the benzene ring and the naphthalene ring system of 2.68 (12)°. There is an intramolecular O—H...O hydrogen bond involving the adjacent hydroxy and carbonyl groups. The molecule has an E conformation about the C=C bond and the carbonyl group is syn with respect to the C=C bond. In the crystal, molecules are linked by bifurcated C—H...(O,O) hydrogen bonds, enclosing an R21(6) ring motif, and by a further C—H...O hydrogen bond, forming undulating sheets extending in b- and c-axis directions. There are π–π interactions between the sheets, involving inversion-related naphthalene and benzene rings [intercentroid distance = 3.7452 (17) Å], forming a three-dimensional structure.