The n-hexane, chloroform, ethyl acetate and ethyl alcohol extracts of the aerial parts of Centaurea ensiformis, endemic to Turkey, have been assessed for antimicrobial and antioxidant activities. The chemical composition of the hexane extract of this plant was determined. The antimicrobial activities on microorganisms, including multiple antibiotic resistant bacteria, were evaluated using the disc diffusion method. The antioxidant activities were determined by using four complementary in vitro assays: inhibition of 2,2-diphenyl-1-picrylhydrazyl radical, total antioxidant activity, and the total amount of phenolic and flavonoid compounds. The structure of the active extract was elucidated by: thin layer chromatography, column chromatography, gas chromatography or gas chromatography-mass spectrometry. The various extracts of C. ensiformis inhibited the growth of tested bacteria. All the C. ensiformis extracts had no effect on the yeasts. The total antioxidant activity increased with the increasing amount of the extracts (20, 40, 80 and 160 g), which contained linoleic acid emulsion. The major compounds of the hexane extract of the plant were caryophyllene oxide (28.72%), spathulenol (17.81%), eudesmol (13.03%) and -bourbonene (8.51%).