In most parts of Nigeria, traditional medicine practitioners and most rural dwellers use plant parts for treatment of ailments without scientific proof. This study was designed to investigate the antimicrobial activities of the aqueous and ethanol root extracts of Anogeissus leiocarpus against Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 10145, Bacillus subtilis NCTC 8236, Staphylococcus aureus ATCC 25923, Candida albicans 24433 and clinical isolates of Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Staphylococcus aureus, Klebsiella spp and Candida albicans. The antimicrobial assays were carried out using the agar ditch diffusion and agar well diffusion methods. Statistical analysis was done using two way anova without replication. The ethanol extract inhibited all organisms and had lower minimum inhibitory concentrations (MIC) compared to the aqueous extract (P < 0.05). Staphylococcus aureus recorded the lowest MIC in ethanol and aqueous extract while Klebsiella spp had the highest MIC in ethanol extract. The aqueous extract had no activity against Candida albicans ATCC 24433. The use of this plant root alone and in combination with other plants by herb medicine practitioners for the treatment of infectious diseases can therefore be justified. However further work should carried out to isolate the active component that furnishes the understudied plant with its antimicrobial potential and as well determine the toxicity of the plant.