Verbascum species are traditionally used in the treatment of respiratory disorders. Orange mullein (Verbascum phlomoides L.) is one of three species that are the official source of drug mullein flower (Verbasci flos). Our study aimed to determine the overall quality of the V. phlomoides flos and V. phlomoides folium, the contents of polyphenols, tannins, flavonoids, and phenylpropanoid derivatives alongside the antioxidant capacity of their ethanolic extracts. Quality control tests were conducted according to monographs of Ph. Eur. 10.0, secondary plant metabolites were quantified spectrophotometrically while the antioxidant potential was estimated by two complementary methods (DPPH free radical scavenging and β-carotene bleaching assay). The higher contents of examined compounds were determined in flower extract although the leaf extract showed a stronger antioxidant capacity. We can conclude that Verbascum phlomoides is a rich source of biologically valuable phenolics, it possesses considerable antioxidant capacity and investigated herbal drugs fulfill pharmacopeia’s quality requirements.