Resumo. The Hymenaea courbaril var. stilbocarpa wood has a high density being employed in construction, carpentry and laminate. The stem exudes a rich terpene resin which can be used in the varnish industry. The endocarp of the fruit is edible and can be eaten raw. The chromosomal duplication of forest species aims to maximize economic interest features, such as those related to the development and forest gain. This study aimed to induce and verify polyploidy in root meristem cells of Hymenaea courbaril through morphological and cytological features. To induce polyploidy, the root meristems were exposed to the trifluralin herbicide at a concentration of 3 μM at 4 ºC for 14 (control), 24, 48, 72 and 96 h. Then, the rootlets were stored for 24 h in a closed flask and refrigerated in methanol: acetic acid solution (high purity) in the ratio 3:1, at -4 ºC. Root meristems were digested in pectinase enzyme (SigmaTM). Mitotic cells were obtained by cell dissociation, air drying and hotplate. 30 cells in metaphase were colored with Giemsa 5% and analyzed. The stomata were obtained from young plantlets of each treatment under the same physical and chemical conditions. For stomata analysis, was used epidermal print of adaxial leaf, with universal instant adhesive (Super BonderTM). 200 stomata were analyzed of each treatment. Among the four treatments evaluated, the exposure of root meristem for 96 h in 3 μM trifluralin, at 4 ºC, induced genome duplication in Hymenaea courbaril L. var. stilbocarpa with 2n = 4x = 48 chromosomes and stomata average size of 0.215 mm, being superior to the other treatments.