The present study was undertaken with the objective of testing the antibacterial and antifungal activities of Cassia fistula leaves and identifies the bioactive compounds. The antimicrobial activity of leaves extract were determined in aqueous and organic extracts, and the minimum inhibitory concentration (MIC) against 6 species of pathogenic & non-pathogenic microorganisms: Bacillus subtilis, Staphylococcus aureus, Salmonella typhi, Escherichia coli, Pseudomonas aeruginosa and Candida albicans using disc diffusion method. The chemical constituents of organic plant extracts were separated by thin layer chromatography (TLC) and the plant extracts were purified by column chromatography and were further identified by Gas chromatography-mass selection (GC-MS) analysis. Significant inhibitory activity was observed with methanol extracts of plants against the test microorganisms while less antibacterial activity was observed in hexane, acetone and aqueous extracts. The MIC of the plant extracts ranged between 1000µg to 2000µg/ml. The methanolic extract of C. fistula leaves had potent anti bacterial and antifungal activities against tested microorganisms.  12 compounds were identified in C. fistula leaves extract by GCMS analysis.  The composition of C. fistula revealed the presence of aliphatic acids and alcohols.