In this study, fatty acid compositions, total phenolic contents, and antioxidant effects of the stem and seed extracts from Euphorbia chamaesyce L. (Euphorbiaceae) were investigated. Linolenic and linoleic acids were found as the main fatty acid components in the seed and stem hexane extracts by using GC/MS. In the seed hexane extracts, linolenic and linoleic acids were found as 32.42% and 15.04%, respectively. On the other hand, in the stem hexane extracts, they were found as 22.31% and 14.25%, respectively. EC/SEM (seed methanolic extract, IC50 = 5.35 +/- 0.01 mu g/mL), EC/SEA (seed acetone extract, IC50 = 8.61 +/- 0.11 mu g/mL), and EC/SEE (seed ethyl acetate extract; IC50 = 20.6 +/- 1.12 mu g/mL) showed higher radical scavenging effect than synthetic antioxidant BHT. The results showed that the seeds of E. chamaesyce had a high amount of polyunsaturated fatty acids and remarkable antioxidant activities.