We studied intraspecific trait variability (ITV) in functional leaf traits of Prosopis pallida trees located in eight populations along a climatic gradient on the Peruvian coast. The objectives were (1) to determine the relative importance of ITV at different ecological scales; (2) to understand how functional leaf traits relate to each other, and (3) to know the main climatic factors related to ITV in P. pallida. We used the restricted maximum likelihood method to decompose the variance across three nested ecological scales (tree, plot, and population level). The relative variance decomposition showed that tree level was the main source of variation for leaf chemical composition and stomatal size and density, whereas the plot and population levels were the main sources of variation for gas exchange and structural variables, respectively. Leaf ITV followed the general trends of the leaf economic spectrum, with negative relationships of leaf mass per area with both photosynthetic rate and leaf nitrogen. Precipitation was not related to any of the leaf traits, while mean annual temperature was correlated negatively with leaf relative water content and positively with water use efficiency. Our results highlight the importance of ITV in P. pallida and the possible impact of climate change.