The chemical composition, antimicrobial, anti-inflammatory, antioxidant and cytotoxic activities of the extracted essential oils (EOs) of capetula and shoots of Senecio glaucus L. were determined. The main constituents are m-mentha-1(7),8-diene (31.4% and 25.6% of total capetula and shoot oils, respectively), cis-m-mentha-2,8-diene (22.9% and 8.2%), dehydrofukinone (17.2% and 19.9%), α-terpinolene (3.9% and 3.1%) and 2,5-cyclohexadiene-1,4-dione,2-(1,1-dimethylethyl)-5-(2-methyl-2-propen-1-yl)-(3.9% and 3.4%). Sabinene constitutes about 2.7% of the capetula EO, but not detected in shoot oil. α-Fenchene and 1,3,8-p-menthatriene represented by 5.6% and 5.3% respectively, in the shoot EO, but not detected in capetula oil. More than half of the oils was monoterpenes, followed by sesquiterpenes. Both EOs differentially exerted antimicrobial effects on Gram-positive and Gram-negative bacteria, yeasts and molds. Capetula oil showed anti-inflammation effect higher than the shoots oil. The EOs showed strong antioxidant effect with EC₅₀ values for scavenging DPPH radical of 1.6 and 1.9 μl/ ml for capetula and shoot EOs, respectively, compared to 16 μg/ ml for ascorbic acid. So, the capetula EO was more potent against human breast cancer cells than shoots EO.