We investigated the aerial part of Filipendula ulmaria (L.) Maxim. during flowering. A chromatographically inseparable crystalline mixture of the previously undescribed quercetin-4′-O-β-galactopyranoside and the known quercetin-3-O-β-glucopyranoside (isoquercitrin) in a 7:5 ratio was isolated from its aqueous ethanol extract via successive solvent extraction and column chromatography. The structure of the new compound was determined using 13C and 1H NMR spectra, confirming the galactose moiety is attached to the C-4′ position of quercetin. No information on the occurrence of quercetin 4′-O-β-galactopyranoside in plants was found in the literature.