The purpose of this study was to evaluate and compare the effects of early (EHVOO) and late harvest (LHVOO) dates on phenolic composition of virgin olive oils (VOO) from the Ayvalik (Edremit) variety. Liquid chromatography combined with a diode array detector and ion spray mass spectrometry in the tandem mode (LC-DAD-ESI-MS/MS) with negative ion detections was used for identification of phenolic compounds in the VOOs. A total of 14 phenolic compounds were identified and quantified in VOOs, including phenolic alcohols (2), phenolic acids (4), secoiridoids (5), and flavonoids (3). Secoiridoids followed by phenolic alcohols and flavonoids were the most abundant compounds of the VOOs. Among secoiridoids 3.4-DHPEA-EDA and 3.4-DHPEA-EA were the most dominant compounds. The antioxidant capacity of VOOs was determined by two different methods, including DPPH and ABTS. The antioxidant capacity of LHVOO was found to be higher than that of EHVOO. Additionally, significant linear correlation was confirmed between the phenolic content and antioxidant capacities of VOOs.