Aims: To assess the fertility island effect of Prosopis pallida in the North Peruvian dry forests and analyze if it is influenced by tree size and structural and/or chemical leaf traits. Methods: We measured the soil nutrient concentrations under and outside the tree canopy in five populations that differ in mean annual temperature and annual rainfall in North Peru. We also measured tree size (height, stem diameter, and crown area), leaf structure (leaf mass per area (LMA) and leaf dry matter content), and leaf nutrient concentrations (C, N, P, Mn, Fe, Cu, and Zn). Results: The concentration of most soil nutrients was higher under the P. pallida canopy. Tree size affected positively the soil C, N, and P concentrations, while leaf structural traits such as LMA were negatively related to the soil C, N, and P concentrations. The relationships between the nutrient concentrations in the leaf and soil were only significant for P and Mn. The tree size effect was greater in those populations where the temperature was lower, suggesting the fertility island effect can be increased or weakened by climatic factors. Conclusions: P. pallida have a significant though limited fertility island effect regulated by plant traits and influenced by climatic factors.