Pistacia lentiscus L. fruits are an excellent source of phenolic compounds endowed with antioxidant activities. Ethanol-water mixtures are in focus for plant extracts preparation due to their acceptability for human consumption. In this study, the effect of ethanol concentration in ethanol/water (EtOH/H2O) extraction solvent on the solubility of target phenolic compounds was firstly predicted using COnductor-like Screening MOdel for Real Solvents (COSMO-RS). Subsequently, the computational results were confirmed experimentally based on extraction yield, phenolic composition, antioxidant activity and RP-HPLC analysis. Extractions were achieved using bead milling by varying EtOH concentrations in order to prepare a suitable extract that could be safely used for food purposes. The obtained results highlighted a good correlation between COSMO-RS simulations and experiments. The highest polyphenol and flavonoid contents (292.04 mg GAE/g DR and 11.07 mg CE/g DR, respectively) were achieved with 70% EtOH, which is in correlation with RP-HPLC quantitative analysis, while the highest anthocyanin content (94.00 mg C3OG/100 g DR) was obtained with 80% EtOH. Concerning antioxidant activity, the best DPPH center dot radical scavenging activity (IC50 = 2.39 mu g/mL) was obtained with 70% EtOH. Reverse Phase High Performance Liquid Chromatography (RP-HPLC) analysis showed that gallic acid was the major compound of Pistacia lentiscus fruits in all EtOH/H2O mixtures. These findings showed that the EtOH/H2O (70/30) mixture is the most suitable to obtain P. lentiscus fruit extracts with the highest phenolic compounds content and antioxidant activity.