ABSTRACT Synergy refers to the combination and interaction of two or more agents which produces a result that is greater than the sum of their individual effects. Hence, the synergistic assessment of the effects of Sida acuta & Citrus aurantifolia, Sida acuta & Dioscorea bulbifera and Citrus aurantifolia & Dioscorea bulbifera combined extracts on selected bacteria (Escherichia coli0157:H7, Salmonella typhymurium and Vibrio cholerae) were investigated. The study area was Omuanwa in Ikwerre Local Government Area of Rivers State, Nigeria were the plants were collected. The test organisms were identified by polymerase chain reaction technique, while the antimicrobial effects of the combined plant extracts were examined against the different bacterial species by agar well diffusion method and sensitivity interpreted in accordance with the Clinical and Laboratory Standard Institute. Phytochemicals extracted were Flavonoids, Cardiac Glycosides, Tannin, Phenols, Alkaloids, Steroids, Terpenoid and Saponins, however, the concentrations of phytochemicals extracted by ethanol and aqueous showed statistical significant difference of p