Abstract: Essential oils or volatile oils from medicinal plants have potentially very strong antimicrobial activities for control of pathogenic microorganisms. Ocimum basilicum is one of the medicinal plants which are widely used as sources of extracts with strong antibacterial and antioxidant properties. In this study, the leaf extract of Ocimum basilicum was tested for its antibacterial activity against some human pathogenic bacteria (Staphylococcus aureus and Escherichia coli). Antimicrobial activity test was carried out by using the hole-plate diffusion method. Plant materials were dried and extracted with 95% ethanol. The tested extract showed very strong antimicrobial activity against both strains. The antimicrobial activity was evaluated by measuring the zone of inhibition. The strongest inhibition activity was observed against E. coli (21 mm zone) at 200 mg mL-1 of leaf extract followed by Staphylococcus aureus which showed 16 mm inhibition zone at 200 mg mL-1 of leaf extract. Physical properties of the extract of Ocimum basilicum were evaluated. The color of the extract is greenish, has intense scent, density is 0.937 g cm-3 at 25°C, refractive index is 1.489 and specific gravity is 0.887.