Lagerstroemia speciosa (L.) Pers. (Lythraceae) has been used in Vietnamese traditional medicine for the treatment of several diseases such as inflammation, obesity, and diabetes. Phytochemical investigation of the methanol extract of Lagerstroemia speciosa aerial parts led to the isolation of two derivatives of ellagic acid, 2,3,7-tri-O-methylellagic acid (3), 2,3,8-tri-O-methylellagic acid (4) and cyclitol (5) together with a two phytosterols Beta-sitosterol (1) and Beta-sitosterol-glucopyranoside (2). Their chemical structures were determined by spectroscopic methods. including FT-ICR/MS and 10 and 20 NMR.