The essential oils obtained by hydrodistillation (HD), steam distillation (SD) and solvent free microwave extraction (SFME) from the stems and flowers of Tanacetum tenuisectum (Boiss.) Podl., which is endemic to Iran, were analyzed by GC and GC/MS. Camphor (26.9 %, 27.2% and 25.5%), borneol (12.6%, 11.5% and 7.6%) and 1, 8-cineole (7.9%, 13.2% and 11.3%) were the main constituents of the HD, SD and SFME oils of Tanacetum tenuisectum respectively. All three oils were rich in regard to monoterpenes and small percentage of sesquiterpenes and non terpenoid compounds. Antibacterial activity of the essential oil of the plant was determined against six Gramm positive and Gramm negative bacteria. The results showed that this oil was active against all of the tested bacteria.