The aim of this study was to determine chemical composition, and evaluate the antioxidant and antibacterial activities of the essential oil from leaves of Cleistocalyx operculatus Roxb. grown in Phu Tho province. The Gas chromatography-mass spectrometry (GC-MS) analyses of the essential oil of Cleistocalyx operculatus Roxb. leaves led to the identification of 21 components. Its major constituents were (Z)--ocimene (60.59%), (E)--ocimene (11.96%), -pinene (9.23%) and myrcene (6,22%). Antibacterial activity assays were performed on the essential oil using the agar well method. The results indicated that the essential oil showed antibacterial effects against Staphylococcus aureus, Pseudomonas aeruginosa and Candidaalbicans, especially Pseudomonas aeruginosa antibacterial ability was much higher than that of cefotaxime as an antibiotic. In the DPPH assay, the essential oil exhibited antioxidant activity with EC50 were 13828g/mL.