The leaves of Psidium guajava is used in folk medicine as an antidiarrhoic in Nigeria and many other countries of the world. It is also employed for the treatment of vertigo and regulation of menstrual periods. World health organization encourages and indicated that studies on medicinal plants should include both identification of chemical constituents and determination of the biological activities of such plants. In this preliminary study, phytochemical and antibacterial properties of crude aqueous extract of Psidium guajava leaf were evaluated. The extract was subjected to qualitative chemical screening for identification of various classes of active chemical constituents while disc diffusion method was used to determine the antibacterial properties of the extract against some gram positive and gram negative bacteria. The extract showed the presence of tannins, saponins, carbohydrates, flavonoids, steroids and cardiac glycosides. The extract inhibited the growth of Salmonella typhi and Klebsiella pneumoniae, but has no effect on the growth of Escherichia coli, Staphylococcus aureus and Streptococcus fecalis organisms. The study revealed some antibacterial properties of the extract that justify the use of the plant in folk medicine. However, further studies need to be carried out to identify the potentials of the plant to be considered as a natural source of antibacterial agent.