Pecan trees require adequate soil moisture conditions to produce nuts with good yield and quality. Irrigation should be an important considered practice in orchards management plan, mainly in regions with water deficit periods. The objective of this research was to evaluate irrigation on pecan nuts growth and yield. This study was conducted in Uruguay, during the fast development phase until the pecan nuts harvest. Three irrigation treatments were used: 0 L (control), 70 L and 140 L plant-1 of water every two days, applied via drip irrigation in seven-year-old pecan trees of the cultivar Success. The number of nuts per cluster and nuts' diameter and length were evaluated during nut growth. After harvesting, peeled nuts' width and length were measured, and after peeling, the kernel length, width, height and filling and the kernel and peel percentage were evaluated. According to the results, it was possible to identify that periods of water deficit during pecan nuts development affected the kernel filling stageand size. Irrigation in pecan plants provides greater dimensions and nuts mass. With the use of 140 L plant-1, there was an increase in the nut mass of more than 100% in relation to the nuts from plants without irrigation.