Phytochemicals are chemical compounds often referred to as secondary metabolites. Forty four bioactive phytochemical compounds were identified in the methanolic leaves extract of Cassia angustifolia. The identification of phytochemical compounds is based on the peak area, retention time molecular weight and molecular formula. Gas chromatography-mass spectrometry (GC-MS) analysis of C. angustifolia revealed the existence of the 2,5-dimethyl-4-hydroxy-3(2H)-furanon, 2-propyltetrahydropyran- 3-ol, estragole, benzene, 1-ethynyl-4-fluoro-, 5-hydroxymethylfurfural, anethole, 7-oxabicyclo[4.1.0]heptan-2-one,6-methyl-3-(1-methylethyl)-, 2-methoxy-4-vinylphenol, 1,2,2-trimethylcyclopentane-1,3-dicarboxylic acid, E-9-tetradecenoic acid, caryophyllene, cholestan-3-ol,2-methylene-, (3?,5?)-, Benzene, 1-(1,5-dimethyl-4-hexenyl)-4-methyl-, ?-curcumene, 7-epi-cissesquisabinene hydrate, Cyclohexene, 3-(1,5-dimethyl-4-hexenyl)-6-methylene-,[S-(R*,S*)]-m, octahydrobenzo[b]pyran, 4a-acetoxy-5,5,8a,-trimethyl, dodecanoic acid, 3-hydroxy, tetraacetyl-d-xylonic nitrile, 1-ethenyl 3, trans(1,1-dimethylethyl)-4,cis-methoxycyclohexan-1-ol, phen-1,4-diol,2,3-dimethyl-5-trifluoromethyl, 5-benzofuranacetic acid, 6-ethenyl-2,4,5,6,7,7a-hexahydro-3,6-dime, 5-benzofuranacetic acid, 6-ethenyl-2,4,5,6,7,7a-hexahydro-3,6-dime, phytol, acetate, desulphosiniqrin, oxiraneundecanoic acid, 3-pentyl-,methyl ester, cis,Phytol, 9,12,15-Octadecatrienoic acid, 2-phenyl-1,3-dioxan-5-yl ester, butanoic acid, 1a,2,5,5a,6,9,10,10a-octahydro-5,5adihydroxy-4-(h), 9-Octadecenoic acid, 1,2,3-propanetriyl ester, (E,E,E) and Diisooctyl phthalate. C. angustifolia was highly active against Aspergillus terreus (6.01±0.27).