Abstract: Antibacterial activities of aqueous and ethanolic extracts of Allium cepa (onion bulb) were investigated against Escherichia coli, Salmonella spp., Streptococcus pneumoniae, Shigella spp., and Staphylococcus aureus with the minimum inhibitory concentration (MIC) of 0.2 g/ml by agar dilution technique. The antibacterial potency of the extract as evaluated by broth dilution technique, showed diameter of inhibition zone of 17.08 mm, 0.00 mm, 19.00, 19.00 and 15.0 mm for E. coli, Salmonella spp., S. pneumoniae, Shigella spp., and Staph. aureus respectively at a concentration of 0.2 mg/ml for aqueous extract and diameter of inhibition zone of 23.0 mm, 20.00 mm, 20.00 mm, 21.00 mm and 21.00 mm for E. coli, Salmonella spp., S. pneumoniae, Shigella spp., and Staph. aureus respectively at a concentration of 0.2 mg/ml for ethanolic extract. The result obtained using the ethanol and hot water extract of the plant showed that the local use of medical plant are based on the efficacy of their active principle which can be discovered scientifically; orthodox medical practices can therefore be complemented with traditional practices.