Leaves are the most variable plant organ, responding and adapting to the environment in the long and short term. However, the link between leaf functional traits and environmental gradients is challenging, especially in systems of high diversity, such as transitional regions between savannas and tropical forests that are considered unstable. Here we evaluate anatomical and morphological traits and nutrient concentrations for the most representative woody species of four vegetation types (i.e., semideciduous forest, cerradão, typical cerrado, and cerrado rupestre) in the Amazonia–Cerrado transition to explore how vegetation will respond to changes in the environment. We found that closed-canopy species invested in traits related to rapid resource acquisition (e.g., higher leaf water content, larger stomata size, and higher maximum opening of the stomatal pore), while open-canopy species optimized traits related to resource conservation and protection from physical damage (e.g., higher leaf thickness, smallest maximum stomatal pore opening and smaller size of stomata). Our study shows that functional traits play an important role in adapting to environmental gradients and help explain the performance of trees in the Amazonia–Cerrado transition, opening the door to a more accurate prediction of plant community responses over time.