The increased rates of microbial resistant to synthetic drugs have paved way for the use of medicinal plant extracts for treatment. Phytochemical screening and antimicrobial activity of Mangifera indica leaves extract on some isolates from dental cavities was studied. The leaves were randomly collected from a local farm in Agbani Nkanu West L.G.A Enugu State Nigeria. The leaf samples were morphologically identified, washed, air dried at room temperature for 48 days and milled into powder with a milling machine in Chemistry Department, Enugu state University of Science and Technology. The solvents used for extraction were ethanol, methanol, N-hexane and water. Ethanol and methanol extracted most of the bioactive ingredients, followed by water and N-Hexane. The phytochemicals screened were; terpenoids, steroids, glycosides, phenols, saponins, tannins and alkaloids. The extracts were divided into dialyzed and undialyzed fractions. The dialyzed fraction was done for 48 hours in a refrigerator. Organisms isolated from dental cavities were; Streptococcus mutans, Escherichia coli, Staphylococcus aureus, lactobacillus spp, Candida albicans. The antimicrobial activity was determined using agar well diffusion method and the result showed that the dialysed extracts of ethanol and methanol had higher sensitivity against the dental isolates than the undialyzed extracts. Streptococcus mutans was the most inhibited organism with inhibition zones of 12mm and minimum inhibitory concentration of 6.25mg/ml. Hence, dialysed ethanol and methanol leaf extracts of Mangifera indica can be used as an adjunct therapy for dental cavities.