Purpose: Water irrigation regimes strongly influence the agrophysiological parameters in pistachio. This study aims to investigate the impact of the partial root drying on the yield, vegetative growth, physiological parameters, water status and biochemical traits of the pistachio cv. Mateur budded on P. atlantica rootstocks during the growing season (2021). Research Method: The agro-physiological responses of the pistachio trees located in the experimental orchard of the Regional Center of Agriculture Research (CRRA, Sidi Bouzid, Tunisia), were studied. Three water treatments were applied; T0: 100% Partial root drying (PRD) during all the season, T1; 75% PRD during all the season and T2; 50% PRD during all the growing season. The leaf gas exchange parameters were determined using a portable photosynthesis system (CI-340 handheld photosynthesis system, USA). Findings: Results showed the stomatal conductance (gS) of pistachio leaves ranged from 320 to 760 mmol H2O m-2s-1 in the 100% PRD treatment whereas the water regimes 75% PRD and 50% PRD presented a clear decrease in this parameter. The proline and the soluble sugar content reached its maximum value (2.10 μmol g−1 FW and 275.60 μg g−1 FW, respectively) under the 50 % PRD treatment during the month of August. Research limitations: No limitations were found. Originality/Value: The 75% PRD treatment was the most efficient as it did not show significant differences with the 100% PRD treatment while 25% of the irrigation water was saved. The partial root drying strategy can be used in pistachio orchards under semi-arid conditions.