In arid and semi-arid areas, farmers are experiencing unprecedented water scarcity, which is likely to increase by the perspective of global warming. The purpose of this study was to evaluate the effect of three irrigation frequencies on vegetative growth, leaf turgor pressure, and photosynthesis of young olive trees (Olea europaea L. cvs ‘Koroneiki’ and ‘Picholine’). We found that throughout the experiment and for all irrigation treatments, Picholine cultivar showed a higher rate of vegetative growth. In addition, the leaf turgor pressure for this cultivar showed fewer signs of stress overall as it recorded less Pp curve inversions during summer. However, during this season the photochemical efficiency in Picholine for the frequencies T1 and T2 were lower than Koroneiki by 9.53% and 10.63%, respectively. Which implied that the non-stomatal limitation of photosynthesis has an impact on Picholine photosynthetic production, which in turn indicates that this cultivar is more sensitive to high temperature. Moreover, irrigation frequency has little effect on the Koroneiki cultivar.