The effect of variation of harvest time and location on the total phenolic content, antiradical scavenging activity and phenolic compounds composition of leaves of Gemlik olive cultivar obtained from two different location (Gemlik and Mudanya in Marmara Region of Turkey) were investigated. It was determined that the highest total phenolic content (373.36 and 336.70) were observed in April for both region. Among the olive leave samples the highest (93.69%) antioxidant activities were determined in olive leaves grown in Mudanya and harvested in December and (93.86%) in either olive leaves grown in Gemlik and harvested in April. Determination of phenolic compounds in olive leaves was carried out by LC-DAD-ESI-MS/MS. The results of analysis phenolic compounds showed that oleuropein content ranged from 94.21 mg/kg to 860.21 mg/kg in olive leaves. Differences were observed in the concentration of phenolic compounds depending on the harvest time and location in all olive leaf samples.