In this study, some physico-chemical and antioxidant properties, volatile compounds and fatty acid composition of ten different onion seeds were investigated. The fatty acid composition and volatile compounds were analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS), respectively. Physicochemical analysis showed that onion seeds possessed high amount of oil (21.86 %-25.86 %) and crude protein (15.7 %-26.1 %). GC results revealed that onion seed oil was rich in linoleic acid (49.42-60.66 %) which was followed by oleic and palmitic acid, respectively. There was a large number of substances such as hydrocarbons, alcohols, acids, esters and sulfur-containing compounds. It could be concluded that onion seeds can be utilized in food industry due to their physico-chemical properties and contents of oil and volatile components.