This study was conducted on the antibacterial, antimycobacterial and antifungal activities of various extracts (petroleum ether (PE), chloroform (CHCl3) and ethanol (EtOH) extracts; infusion and decoction) and essential oil from the aerial parts of S. cassia Sam. ex Rech.f. and the chemical composition of the most active samples. The antibacterial activity was determined against Bacillus subtilis, Staphylococcus aureus, methicillin resistant Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus faecalis, Klebsiella pneumoniae, Proteus mirabilis and Escherichia coli. The antimycobacterial activity was analyzed against five different Mycobacterium tuberculosis and the antifungal activity was compared with two dermotophytes and three Candida species. The composition of EO was analyzed by GC-FID and GC-MS. The EO had a very good activity against B. subtilis (0.3 mu L/mL) and good activity against S. aureus, methicillin resistant S. aureus (MRSA) and E. faecalis (0.6 mu L/mL). All extracts were active in the antimycobacterial and antifungal tests (MICs=50-400 mu g/mL). The EO was the most active samples against all Mycobacterium strains, dermatophytes and Candida species (MICs=0.1-6.25 mu L/mL). Because of the high activity of EO, its composition was analyzed, and the major compound was found caryophyllene oxide (22.3%), which was also found the major components of the essential oils from other antimicrobial plants such as Salvia trichoclada Benth.