Antimicrobial activity of the methanolic extract and fractions of Lumnitzera racemosa was evaluated against fungi, virus and pathogenic bacteria. Crude methanolic extract and n-butanol fraction were ineffective against fungi and virus tested but exhibited significant bactericidal activity on all the bacteria tested. Flavonoids, quercetin and myricetin are the main active constituents with quercitrin, quercetin-3O-hexoside, kaempferol 4’-methyl ether, kaempferol-3,4?dimethyl ether, and bi-isorhamnetin and myricetin-7O-methylether(3 - 8”)quercetin -3O-rhamnoside, which are also constituents of the active fraction being partly responsible for the observed activity. Myricetin showed the most potent activity (MIC - 1.5 mu g/ml) against Pseudomonas aeruginosa being markedly active against others (MIC - 6 mu g/ml). Based on the current findings it can be concluded that this plant has antibacterial activity