BACKGROUND: Chemotherapeutics like 5-fluorouracil (5-FU) may induce a variety of adverse effects, including oral mucositis (OM), which may necessitate treatment discontinuation in patients with cancer. Currently, only a few models of OM are available for studying many aspects of pathophysiology and treatments. AIM: The current study examined the clinical and histological aspects of 5-fluorouracil-induced oral mucositis (5FU-OM) in rats. METHODS: We randomly divided 19 male Sprague-Dawley rats into 8 healthy rats and 11 that received a single dose of 5FU-OM. On the first day of the experiment, the 5FU-OM group was administered an intraperitoneal injection of 5-FU (150-mg/kg BW), whereas the healthy group was not administered the drug. The third day involved scratching the oral mucosa of all rats in both groups. Clinical observations included changes in body weight, food consumption, hair loss, and severity of oral lesions. At the end of the study, we collected cardiac blood and mucosal tissue samples to investigate hematological and histological alterations. RESULTS: Our findings demonstrated that a single intraperitoneal injection of 5-FU and mucosal irritation might result in ulcerative OM. We discovered other clinical toxicities caused by chemotherapy, such as weight loss, red lacrimation, facial edema, epistaxis, and hair loss. 5-FU also produced hematological abnormalities, including anemia and thrombocytopenia. Histopathological changes included ulceration, bleeding, vasodilation, edema, and inflammatory cell infiltration. CONCLUSION: This simple rat model of OM accurately replicates the clinical and histological mucosal responses to chemotherapy, including its systemic adverse effects. Thus, it can be used in research on OM.