Uapaca pilosa(Hutch.) a plant used in some parts of Africa in the treatment of dysentery, menstrual pain, fever, constipation, erectile dysfunction, skin infections, female sterility, pile, rheumatism, emetic, tooth-troubles and fatigue. The dried plant was extracted, the extract was subjected tophytochemical investigation using standard method revealed the presence of alkaloids, flavonoids, anthraquinones, tannins, saponins, steroids, terpenoids and glycocides. Extensive silica gel column chromatography of the ethylacetate fraction of the stem bark extract, the most active of all the fractions, led to the isolation of two compounds GF1 and GF2. Their identities were determined by analysis of their spectral data using FTIR, 1D and 2D NMR. The structures of the compounds were supported by comparing their spectral data with the literature. GF1 was found to be betulin while GF2 was found to be beta-sitosterol. The antimicrobial screening of the crude extract and fractions using agar well diffusion methodshowed activity against Staphylococcus aureus, Shigella dysenteriae, Salmonella typhii, Bacillus subtilis and Escherichia coli. The Zone of Inhibition of the plant extract against selected microorganisms ranges from 13mm to 17mm against Staphylococcus aureus, 10mm to 14mm against Bacillus subtilis, 12mm to 15mm against Shigella dysenteriae, 15mm to 18mm against Escherichia coliand 10mm to 11mm againstSalmonella typhii. The MIC and MBC for the extract, fractions and isolated compounds were also determined. The range of Minimum Inhibitory concentration is between 6.25 mg/mL to 25 mg/mL for Staphylococcus aureus, 25 mg/mL for Shigella dysenteriae, 6.25 mg/mL for Bacillus subtilisand 12.50 mg/mL for Escherichia coli while the Minimum Bactericidal Concentration range between 12.50 mg/mL for Staphylococcus aureus, 50 mg/mL for Shigella dysenteriae, 12.50 mg/mL for Bacillus subtilis and 25 mg/mL for Escherichia coli. This study on the stem bark extract from Uapaca pilosa, used traditionally in some parts of Africa as a medicinal plant for the treatment of various ailments has confirmed that it has antimicrobial activity against the microbes that cause some of these diseases.