Pistachio acreage is increasing noticeably in Spain. However, water management in these plantations still remains a challenge due to the fact that irrigation in new production regions is still not well defined. In this context, the current study aimed to assess the impact of two contrasting irrigation doses on the water relations, yield, and nut quality of pistachio trees (cv. Kerman) in La Seca (central Spain) over five years. Specifically, the high irrigation treatment (H) received 50% more water than the control (C). Soil moisture, stem water potential (Ψs), gas exchange parameters, growth, yield, and nut quality traits were monitored. During summer, a slight decline in Ψs was observed, with trees from the C treatment exhibiting the most negative values, indicating a slight dehydration. The dry weight of split nuts, with greater marketing value, was higher in H compared to C over the five-year study period. In general, the nutritional composition of the nuts did not differ between treatments. These results provide useful information for the establishment of a suitable irrigation strategy for pistachio cv. Kerman in central Spain and other regions with similar weather conditions.