Purpose: This study aimed to evaluate the effect of local and intravenous administration of adipose tissue-derived stem cells on the regeneration of oral epithelium in chemotherapy-treated rats. Material and Methods: 48 adult male albino rats were used in this study throughout the experimental period (2 weeks). 12 rats were left as negative controls (G I) and the remaining experimental 36 rats were treated with 5-fluorouracil (chemotherapeutic agent) in a dose of 50 mg/kg/dose to induce oral mucositis. Moreover, acetic acid was injected in the buccal mucosa to produce ulcers and then the rats were subdivided into three subgroups, (G II) in which 12 rats received no treatment, (G III) in which 12 rats received a direct injection of a single dose of adipose-derived stem cells, (G IV) in which 12 rats received an intravenous injection of a single of adipose-derived stem cells. All rats were euthanized; cheek epithelium was dissected and processed for hematoxylin & eosin evaluation. Results: Group III produced better healing than group IV where the ulcer appeared covered with a continuous layer of regenerated epithelium after one week in group III while the regenerating epithelium failed to cover the ulcer in group IV. After two weeks, the epithelium covered the ulcers in both groups but the C.T. architecture appeared better in group III. Conclusion: The direct injection of ADSCs in oral mucositis produces faster healing potentiality than intravenous injection.