Background. Oral mucositis is the most debilitating and troublesome adverse effect of irinotecan (CPT-11) treatment. It adversely affects the patient quality of life. The aim of this work was to study the histological, immunohistochemical, and molecular changes in the oral mucosa by CPT-11 and the possible alleviated role of atorvastatin. Methods. Rats were randomly divided into control, CPT-11-treated group, and CPT-11+ atorvastatin-treated group. At the end of the experiment, the anterior two-thirds of the tongue was dissected out and divided into two parts: one part for light microscopic examination and the second for molecular study. Results. CPT-11-treated group revealed loss of normal mucosal organization, areas of ulceration and inflammation, and loss of architecture of lingual papillae. A significant decrease in immunohistochemical and molecular gene expression of Ki-67 and antiapoptotic Bcl-2 levels was observed. A significant increase in NF-κB immunohistochemical and mRNA gene expression level and a nonsignificant increase in Nrf2 gene expression were detected. Coadministration of atorvastatin showed remarkable improvement in the histopathological picture with a significant increase in Ki-67 and Bcl-2, a significant decrease in NF-κB protein and gene expression, and a significant increase in Nrf2 gene expression. Conclusion. Atorvastatin substantially attenuates CPT-11-induced oral mucositis through the initiation of the antiapoptotic gene, modulation of the inflammatory, and antioxidant gene expression.