Background and Objective: Oral submucous fibrosis (OSF ) is a precancerous disease that ischaracterized by subepithelial fibrosis of the oral cavity. Bleomycin is a chemotherapeutic antibioticwhich was used in animal models of pulmonary fibrosis as fibrosis is one of the major side effectsof Bleomycin in human cancer therapy. The aim of this study was to evaluate the degree of fibrosisin OSF induced by Bleomycin in a rat model using Van-Gieson stain and studying the expressionof TGF‑ β1 and SMAD -3.Materials and Methods: A total of fifty adult female albino rats were used and divided into fourtest groups (ten animals each) according to the duration of treatment (2, 4, 6 and 8 weeks). Anotherten animals were used as control group. Bleomycin at a concentration of 1mg/ml was maintainedand was injected subcutaneously into one side of the cheek mucosa of the rats daily. Meanwhile, therats of the control group were injected with saline. Then the dissected buccal mucosae of the ratswere evaluated by H&E stain, Van-Gieson special stain, TGF‑ β1 immunostaining and determinationof SMAD-3 gene level by qRT -PCR.Results: The histological findings were similar to that of OSF in humans. The mean value ofeach of Van-Gieson, TGF‑ β1 in addition to SMAD -3 gene expression gradually increased by timeto reach its highest level at 8th week of the experiment. Meanwhile, the lowest mean area percentwas recorded in the control group.Conclusion: The histological changes induced by Bleomycin in a rat model gave a fibroticresponse similar to that of OSF in humans. Downregulation of TGF -β1/SMAD -3 signaling couldprovide a valuable method for treatment of OSF.