This study aimed to determine the effect of the maturation degree on the chemical composition of Pistacia atlantica fruits oil. A total number of 21 samples of fruits at three stages of maturation (unripe, middle maturity, and ripe fruits) were used in this study. Thus, the fatty acid composition was studied; the percentage of the unsaponifiable matter (w/w) and its anti-DPPH (2,2-diphenyl-1picrylhydrazyl) activity were assessed. The total phenolic compound content was also evaluated. The obtained results indicated, for the first time, that unripe fruits oil was characterized by richness in linoleic acid (31.63% AE 3.64%), in unsaponifiable matter (9.29% AE 6.19% w/w), and in phenolic compounds (2.51 mg per 100 g oil). For ripe fruit oil, these values were similar to those of some seed oils (22.41% AE 3.66%, 2.98% AE 1.71% w/w, and 0.13 mg per 100 g oil, respectively). Data analysis by principal component analysis showed that linoleic acid percentage and the unsaponifiable fraction percentage could constitute good markers for these fruits. These two parameters associated with a high level of phenolic compounds seem to distinguish and value the oil of P. atlantica unripe fruits. Thus, the findings revealed that the unripe fruits, rich in bioactive molecules such as unsaturated fatty acids and phenolic compounds, would be the optimal stage of harvesting time. Based on this, we could integrate this natural bioresource in industrial applications. J Am Oil Chem Soc (2019) 96: 903-910The code is composed of a number indicating the site, a first letter indicating the tree (if there is more than one per site) and letters in brackets indicating the color of the fruit. In the case where second picking on the same tree is performed an additional sign (') was added. 904J Am Oil Chem Soc J Am Oil Chem Soc (2019) 96: 903-910