The study will present results of chemical analysis of mass spectrometry, evaluating the content of pigments in M. domestica leaves dyeing solution and in dyed woollen yarn nowadays. Yarn was dyed with fresh leaves of M. domestica tree. Before dyeing the yarn was treated with potassium aluminium sulphate mordant. Dyestuffs from the yarn were extracted in compliance with modified hydrochloric method of hydrolysis. Extracts were analysed by ultra high-performance liquid chromatography coupled with a diode array detector and mass spectrometry (UHPLC-DAD-MS) for identification of the pigments. Phytochemical screening of dyeing solution of the M. domestica leaves showed presence of dihydrochalcones (phloretin, phlorizin), flavan-3-ols (dimeric B type proanthocyanidin, catechin, epicatechin, gallocatehin, epigallocatechin), flavanols (quercetin derivatives: hyperoside, rutin, quercetrin), phenolic acids and other compounds.