Essential oil composition of aerial parts of the three ecotypes (Koohrang, Bazoft, and Samsami) of wild celery (Kelussia odoratissima) were determined, using GC/MS. The 22 constituents, corresponding to 95.55% of the essential oil of Bazoft ecotype, were identified, of which the major ones are such as z-ligustilide (47.31%) and 3-e-butyl phthalide (17.38%). In the Koohrang ecotype, 24 compounds were identified as 90.38% of its essential oil (the main compounds composed of z-ligustilide (33.73%) and 3-e-butyldiene phthalide (20.1%)). In the Samsami ecotype 24, compounds representing 93.64% of its essential oil were identified, and the main compounds were z-ligustilide (37.55%) and 3-e-butyl phthalide (19.92%). Overall, the analyses showed that z-ligustilide was the major compound that has been reported to have a positive impact on the nervous system, blood pressure, and cholesterol.