The present study was conducted to determine the biochemical characteristics of Fraxinus ornus subsp. cilicica, seeds, an endemic tree species of Turkey. Seeds were collected from three provenances (Diizici-Osmaniye, Andirm-Kahramanmaras, Pozanti-Adana) Seed reserve composition (total soluble sugars, reducing sugars, carotenoids, xanthophylls, total soluble proteins, total tocopherol, total soluble phenolics, flavanoids and oil content) and seed fatty acids contents were examined. Total soluble sugars content and total tocopherol contents of seed among provenances did not differ significantly but other seed constituents were different among provenances. The highest amount of fatty acids present in F. ornus subsp. cilicica seeds were linoleic and oleic acids. The present study is the first report dealing with various aspects of seed composition and should provide valuable information for this endemic species.