Resumo. The anatomical knowledge of species of the Theobroma genus is important for the establishment and maintenance of germplasm collections, considering agronomic and phytopathological studies, and breeding programs. This study aimed to characterize the anatomy of Theobroma speciosum leaves, recording the structural differences observed between sun and shade leaves. Theobroma speciosum leaves were collected at Juruena National Park and in pastures in the rural municipality of Alta Floresta – MT. We analyzed the thickness of the leaf mesophyll, palisade and spongy parenchyma, midvein and vascular bundle. Cluster analysis was performed using the Hierarchical UPGMA method, based on the standardized mean Euclidean distance. Were observed glandular trichomes, claviforme type and sessile stellate, the epidermis is uniseriate in cross section, the mesophyll is dorsiventral, however the parenchymas are little different. Collateral vascular bundles are dispersed in the mesophyll, forming sheaths that extend up to the epidermis. The midvein, in cross section, has a biconvex shape, with closed vascular system surrounded by sclerenchymatic sheath. The constitution of the leaves mesophyll varied with the environment. Plants exposed to full sunlight showed longer cells in the palisade parenchyma, spongy parenchyma with more layers and higher quantity of trichomes, whereas shade leaves showed cells with many mesophyll intercellular spaces. The dendrogram showed the formation of two distinct groups: group I comprises the plants of the Park and group II pasture plants. The clustering showed significant anatomical changes caused by variations of light intensity on leaves, which revealed a large adaptive capacity of Theobroma speciosum .