In this study, a detailed phytochemical investigation of compounds in the twigs of the mistletoe Loranthus europaeus Jacq., which belongs to the Loranthaceae family, is presented. Specimens were collected from the mistletoe L. europaeus growing on oak trees in the mainland of Greece. The alliance of oaks and mistletoes became a symbol of knowledge and strength for many centuries. Although numerous compounds of aerial tissues of other mistletoes, e.g., Viscum album, have been published, few studies have been conducted to investigate the metabolic and physiological traits of the hemiparasitic, deciduous Loranthus europaeus. LC-HRMS-based analysis led to a detailed characterization of ethyl acetate and dichloromethane extracts of the twigs of L. europaeus, which, to the best of our knowledge, exhibit enhanced antioxidant potential. Hence, twenty-four and twenty-six compounds were tentatively identified from the ethyl acetate and dichloromethane twigs’ extracts, respectively; these compounds belong to fatty acids, flavonoids, and flavonoid glycosides. Also, chlorophyll, soluble sugar, starch, and lipid contents in the twigs of L. europaeus, which have not hitherto been published, were investigated.