Bioassay guided phytochemical investigation of petroleum ether, chloroform and ethyl acetate fractions obtained from biologically active total alcoholic extract of stem bark of Albizia lebbeck L. Benth led to isolation of nine known compounds including lupenone (1), freidelin (2), lupeol (3), sapiol (4), mixture of β-sitosterol & stigmasterol (5), β sitosterol- 3-O-glucoside & stigmasterol -3-O-glucoside mixture (6), stigmasterol -3-O-glucoside (7), luteolin (8) and rutin (9). Their structures were established on the basis of spectroscopic methods including UV, MS, IR, 1H &13C NMR, 1H 1H COSY and through comparison with published data and authentics. Compounds 6-8 were isolated for the first time from A. lebbeck. Qualitative estimation of the phenolic and flavonoidal contents of different extracts showed that the plant is rich in phenolic and flavonoidal contents. The major phenolic and flavonoid compounds were detected in ethyl acetate fraction and identified as e-vanillic acid (15079.44 ppm), luteolin (6024.92 ppm) and quercetrin (3120.15 ppm) respectively. GLC/MS analysis of unsaponifiable matter of A. lebbeck, revealed nineteen compounds constituting 55.8% of the total unsaponifiable matter were identified. In addition the GLC analysis of fatty acid methyl esters revealed the presence of 13 fatty acids, ten of which were identified and constitute 91.44 %. Moreover the different A. Lebbeck stem bark extracts showed variable promising strengths in anti-inflammatory, analgesic, antioxidant, cytotoxic and antimicrobial activities.