The phytochemical screening, antibacterial and toxicological activities of extracts of the stem bark of Acacia senegal were investigated. The phytochemical analyses according to standard screening tests using conventional protocols revealed the presence of tannins, saponins and sterols in the stem bark of the plant. Alkaloids, glycosides and flavonoids were not detected in the plant. In-vitro agar diffusion sensitivity tests of crude extract fractions of the plant extracts using ethanol, chloroform, methanol, petroleum ether, water and ethyl acetate were investigated on nine bacterial isolates. Ethanol and methanol stem bark extracts exhibited antibacterial activity on Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus vulgaris, Salmonella typhi, Shigella dysenteriae and Escherichia coli except on Staphylococcus aureus, Streptococcus pneumoniae and Streptococcus pyogenes. The other extract fractions showed no activity on the bacterial isolates at the concentration used. The minimum inhibitory concentration and minimum bactericidal concentration studies revealed that some bacterial isolates were inhibited at concentrations of about 50mg/ml and killed at 400mg/ml. Toxicity studies of the ethanol extracts revealed that they exhibited no significant toxicity (LC50 of 100μg/ml) against Artemia salina . These results suggest that the plant may not be toxic to man and could be a potential source of novel antibacterial compound.