The title compound, C17H19NO4, was synthesized by the reaction of 7-(di-ethyl-amino)-2-oxo-2H-chromene-3-carb-oxy-lic acid with allyl bromide and purified by flash column chromatography on silica gel. Crystals suitable for single-crystal X-ray diffraction were obtained by recrystallization from acetone. The aromatic core of the mol-ecule is not planar with the di-ethyl-amino group and with the carboxyl group that are rotated out of the 2-oxo-2H-chromene plane by 6.7 (2)° and 11.4 (2)°. The NC2 unit of the di-ethyl-amino group is planar with an angle sum close to 360°. Inter-molecular Car-H⋯Ocarbon-yl inter-actions lead to the formation of chains parallel to the b axis. X-ray powder diffraction analysis proves that the title compound was obtained as a pure phase.