Marrubium globosum Montbr. et Auch. ex Benth. ssp. libanoticum Boiss. (Lamiaceae) is a medicinal plant used for the treatment of inflammatory diseases, asthma, coughs and other pulmonary and urinary problems. The goal of our study was to assess the biological activity of M. globosum testing the methanol extract of aerial parts for its antibacterial activity against bacteria known to cause respiratory, gastrointestinal, skin and urinary disorders; the extract showed antibacterial effects against all the strains of bacteria used. A purification of this active extract showed the presence, as main constituents, of verbascoside, isorhamnetin 3-O-beta-D-rutinoside, quercetin 3-O-beta-D-rutinoside, naringenin 7-O-beta-D-glucoside, kaempferol 3-O-beta-D-rutinoside, isorhamnetin 3-O-beta-D-glucoside, quercetin 3-O-beta-D-glucoside, apigenin 7-O-(3''-p-coumaryl)-glucoside, p-methoxy-cinnamic acid, kaempferol 3-O-beta-D-glucoside and apigenin 7-O-beta-D-glucoside. The pure compounds were tested for their antibacterial activity; quercetin 3-O-beta-D-rutinoside, verbascoside and naringenin 7-O-beta-D-glucoside showed the greatest activity.