Abstract The methanol rootbark extract of Combretum glutinosum was subjected to preliminary phytochemical screening and in vitro antimicrobial tests. The methanol rootbark extract revealed the presence of flavonoids, tannins saponins, alkaloid and cardiac glycosides using standard procedures. The antimicrobial activity of the plant extract was assayed by the agar plate disc diffusion and nutrient broth dilution techniques. Test microorganisms which were laboratory isolates include Escherichia coli, Shigella dysenteriae, Bacillus subtilis, Corynae bacterium species and Aspergillus niger. The antimicrobial activities were shown to be concentration-dependent. The extract inhibited the growth of some of the test organisms; the highest diameter of inhibition zone of the crude flavonoids fraction was exhibited by Corynae bacterium species had 30.33±0.58 mm followed by Shigella dysenteriae; the crude saponins fraction was effective towards Escherichia coli with mean inhibition diameter of 19.67±0.58 mm. The extract couldn’t inhibit the growth of Bacillus subtilis as well as Aspergillus niger at the tested concentrations of 100, 50 and 25 mg/ml. However, the crude flavonoids fraction inhibited the growth of Bacillus subtilis at all concentrations with mean values of 25.00±0.00, 22.67±0.58 and 19.33±0.58 mm respectively at concentrations of 100, 50 and 25 mg/ml. Therefore, it is pertinent to say that the activities against bacteria by this plant extract may be due to flavonoids part of the extractives. More so, this study has justified the traditional use of this plant for the treatment of some infectious diseases whose causative agents are some of the organisms tested in this study.