This study aims to evaluate the chemical composition and biological effects of an endemic Algerian species Myrtus nivellei belonging to the Myrtaceae family. The aerial parts of the plant were submitted to hydrodistillation and analysed with gas chromatography - mass spectrometry (GC-MS). This oil was yielded 0,75% (w/w). The GC-MS revealed that 1,8 cineole is the most abundant component (53,44%) while other compounds were present in high contents: 2,2,6,7-tetramethyl-10-oxatricyclo [4.3.0.1(1,7)]- decan-5-one (11,73%), trans ocimene (7,54%), linalyl propirionate (6,81%) and lavandulyl acetate (5,24%). In addition ethanolic extract of studied plant was prepared. Total phenol, tannin, flavonoid, and condensed tannin?s contents were determined using Folin-Ciocalteu, aluminum chloride and vanillin colorimetric methods, respectively. Three tests were used for the investigation of antioxidant activity of both extract and oil. Strong antioxidant activity was shown mainly by crude extract. Antibacterial screening was evaluated against Gram positive and Gram negative bacteria. Ethanolic extract and oil were active especially against Staphylococcus aureus.