A comparative study of the ethanolic extract of the leaves and roots of Landolphia owariensis were subjected to phytochemical screening and antimicrobial activities on E. coli , Staphylococcus spp. and Proteus spp. using dehydrogenase assay method. The phytochemical screening indicated the presence of alkaloids, flavonoids,saponins and tannis in both leaf and root extracts with cyanogenic glycosides present in the root extracts. When the bacterial isolates were exposed to both extracts at different concentrations (20-200 μg/ml) in nutrient broth, their response was concentration dependent.In all the bacteria isolates dehydrogenase activity was progrssively inhibited at concentration of 20μg/ml – 200μg/ml for the leaf and 150 –2500 μg/ml for the root extracts respectively, with total inhibition observed from 700 μg/ml for Proteus spp. and 1800 μg/ml for E. coli for the leaves extract while total inhibition was observed from 2000 μg/ml for both Staphylococcus spp. and Proteus spp. and 2480 μg/ml for E. coli. The observed antimicrobial properties was believed to be due to the presence of alkaloids, flavonoids and tannins, which were identified in the leaf and root extracts. The findings may be of clinical relevance and further substantiates the traditional use of L.owariensis leaves and roots as antimicrobial agent.