ABSTRACT External factors can interfere with the structure and biological activity of plants. Nevertheless, the susceptibility of plants to specific environmental conditions varies, which raises many questions about the behavior of medicinal plants when grown in urban areas. This study aims to detect possible changes induced by exposure of Eugenia uniflora L. to an urban environment, with emphasis on variation in external and internal leaf structure and differences in the production of its main metabolites. We compared leaves of E. uniflora cultivated in forest and urban sites and analyzed them for structural plasticity and characteristics indicative of stress in the urban environment. The leaves of the urban site revealed necrosis and reddish spots, higher stomatal density, smaller stomata and more numerous crystals and secretory glands, as well as evident storage of starch, lipids, and mucilage. The presence of numerous crystals had a high plasticity index and great potential as anatomical marker for evaluating the effects of the urban environment. Visual symptoms and anatomical changes were efficient at diagnosing stress in E. uniflora, while characteristics of the urban site, such as temperature, heat and pollution, are thought to be responsible for the observed variation and may influence your medicinal characteristic.