Oral lesions that manifest as ulcer lesions are quite common and can cause discomfort to the patient. Searching for drugs to accelerate the healing of these lesions is nonstop process. Bixin is a molecule found in annatto (urucum) seeds and is considered a viable therapeutic option to treat such lesions due to its anti-inflammatory, anti-oxidant, and healing properties. Therefore, the present study aimed to evaluate the effect of the bixin solution in the ulcer healing process in the oral mucosa of rats. Ulcers were induced with punches of 0.5 cm in the middle of the dorsum of the tongue of 64 Wistar rats. The animals were randomly divided into 8 groups, in which 4 groups were treated with saline solution, while the other 4 were treated with the bixin solution. The animals were sacrificed in the periods 2, 7, 14, and 21 days after the beginning of the treatment. The species were histologically processed and stained with hematoxylin/eosin and picrosirius. Fibroblasts, reepithelialization, and wound contraction could be observed, as could the quantification of neutrophils, macrophages, plasma cells, lymphocytes, and mature and immature collagen. On the seventh day, the experimental group, when compared to the control group, presented a higher proliferation of fibroblasts, more advanced reepithelialization, and a higher contraction in the wounds. A reduction in the average number of neutrophils in the experimental group, when compared to the control group, could be observed in all periods (p=0.000). Up to two days, the total collagen area was higher (p=0.044) in the experimental group (4139.60±3047.51t han in the control group (1564.81±918.47). The deposition of mature collagen, on the 14(th) day, was higher (p=0.048) in the experimental group (5802.40±3578.18) than in the control group (1737.26±1439.97). The results found in the present study indicate that the bixin solution inhibits the acute inflammatory response with a minor average number of neutrophils and accelerates reepithelialization, wound contraction and collagen maturation, thus illustrating that this solution does in fact represent an important adjuvant in the treatment of ulcers.