Avicennia officinalis L., Avicenniaceae (or Acanthaceae), is a wide spread plant in mangrove forest in Vietnam, Cambodia, Thailand, Indonesia and so on. Some parts of this plant such as barks, leaves, and fruits of A. officinalis have been traditionally used as an aphrodisiac, diuretic, hepatitis, and leprosy treatment. Avicennia officinalis’s chemical compositions remain mostly unknown and have not even been studied in Vietnam. Therefore, we now report on the isolation and the structural elucidation of four flavonoids from this plant growing in Can Gio mangrove forest in Ho Chi Minh City. The crude extract was obtained by the maceration of air–dried powder of leaves with methanol and then evaporation at reduced pressured. This crude extract was separated to three difference extracts including n-hexane, ethyl acetate and remaining aqueous residue by liquid-liquid partition. The ethyl acetate extract was applied to normal and reversed phrase RP-18 silica gel column chromatography and preparative thin layer chromatography to give four compounds. The chemical structures of these compounds were elucidated by 1D-, 2D-NMR spectroscopic and HR-MS analysis as well as compared with data in the literature. They are chrysoeriol 6"e"e-(3"e"e"e,5"e"e"edimethoxycoumaroyl)-7-O-β-D-glucopyranoside (1), luteolin 7-Oβ-D-glucopyranoside (2), 3"e-methylluteolin 4"e-O-β-Dglucopyranoside (3), and flavogadorinin (4). Among them, (1) is a new compound. Further studies on this species are in progress.