Eucalyptus globulus, a plant from family myrtaceae, commonly known as blue gum, grows well in different parts of world and has been known since decades because of its rich ethanomedicinal and therapetic importance. Various phytochemicals isolated from the plant has been well known to possess various pharmacological effects. The aim of this study is to determine the chemical composition and antimicrobial properties of the essential oils of Eucalyptus globulus grown in Haramaya university main campus, Ethiopia. A total of twenty one compounds were identified from the essential oil, by Gas chromatography mass spectroscopy representing 99.85 % of the total oil.The dominant compounds being Eucalyptol (1,8-cineole) 62.38%, α- pinene 23.79% ,α-terpinyl acetate 5.41%, globulol 1.68%, β-pinene 1.1% . The results of the antimicrobial activity tests revealed that the essential oil of E. globulus has antimicrobial activity, especially against Staphylococcus aureus, and Staphylococcus epidermidis. Minimum inhibitory concentration (MIC) for the oil ranged from 0.72 to 2.75 μl/ml.