The essential oil of Teucrium stocksianum Boiss. subsp. stocksianum leaf grown in Oman was analyzed by GC-MS. Forty seven components amounting to 76.1% of the total oil were identified. The major constituents were α-cadinol (7.6%), β-selinene (6.4%), trans-verbenol (5.9%), caryophyllene oxide (5.7%), α-phellandren-8-ol (5.0%), verbenone (5.0%) and δ-cadinene (5.1%). The antimicrobial activity of the oil was tested against a panel of seventeen bacterial and six fungal strains by the disc diffusion method. The oil inhibited the growth of all test organisms at various levels; however, it showed significant inhibitory activity against Staphylococcus and Streptococcus species, as well as yeasts. The minimal inhibitory concentrations (MIC) were also determined.