Abstract The essential oil of Tanacetum macrophyllum growing wild in Turkey was obtained by hydrodistillation, and antimicrobial activity of the essential oil was tested against six bacteria and two yeasts including Candida albicans and Aspergillus niger by disc diffusion method. Further the oil of this plant was analyzed by GC and GC/MS technique. Best effect of the oil was against pseudomonas earuginosa. Twenty-eight components, representing 95.6% of the total oil, were identified. The main component of the oil was Î²-eudesmol (89.5%). The antioxidant activity of the essential oil was measured by the ferric reducing antioxidant power (FRAP) assay. Key Word Index: Tanacetum macrophyllum essential oil componentsantimicrobial activityantioxidant activity