Background: The nutritional value and health-promoting properties cause the fruits (acorns) of Quercus ilex to have great potential for use in the food industry as functional ingredients and antioxidants source. Objective: In this study, the amount of total phenolic compounds, flavonoids in different extracts (defatted, non-defatted) and composition of fatty acids in the fruits oils of Quercus ilex were investigated. Besides, antioxidant activity was determined. Material and Methods: Fatty acids were extracted with n-hexane and determined by gas chromatography with mass spectrometry detection (GC-MS). Total phenolic and flavonoids contents in the extracts were measured spectrophotometrically and the antioxidant activities were tested by the DPPH (2,2-diphenyl-1-picrylhydrazyl), free radical scavenging assay, free radical-scavenging ABTS and total antioxidant capacity. Results: The amount of total phenolic and flavonoid compounds in the defatted Q. ilex were 634.36±27.41 mg GAE/g DW and 96.85±2.13 mg RE/g DW, respectively. Unsaturated fatty acids were detected in higher amounts than saturated fatty acids. The primary unsaturated fatty acids of the Quercus ilex oil were oleic acid (65.38%), 9,12-octadecadienoic acid (16.64%) and palmitic acid (12.81%). Besides, defatted Q. ilex extract showed remarkable DPPH and ABTS radical scavenging activity with IC₅₀ values of 0.008±0.0008, 0.005±0.001 mg/ml respectively, while high total antioxidant capacity of the non-defatted extract with VCEAC value 0.13±0.006. Conclusions: Q. ilex oil contained high amounts of polyphenols, high essential fatty acids and antioxidant potential for producing specific health promoting antioxidants in food and pharmaceutical industry.