Among the acute and chronic lung diseases, pulmonary fibrosis (PF) is the most fatal one because of its prognosis and treatment is so far an unsuccessful task. In this study, we have used the well-known pulmonary fibrosis model, Bleomycin (BLM), to induce PF in Wistar rats. A single intratracheal instillation (3U/Kg BW) of BLM had been administered in fibrosis induced groups. The treatment drug daidzein (0.2mg/KgBW) was administered by subcutaneous mode for 7 days. BLM administration reduces the bodyweight, antioxidant status (enzymic antioxidants such as superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and non-enzymic antioxidants such as vitamin A, vitamin C, vitamin E and reduced glutathione) whereas, it increases the lung wet to dry ratio, hydroxyproline content, collagen deposition, lipid peroxidation and myeloperoxidase. Daidzein treatment improves the body weight, enzymic and non-enzymic antioxidant status and decreases the collagen deposition in lung as confirmed by Masson’s trichrome and Picro-sirius red staining. Daidzein treatment restored the lung architecture as revealed from histopathological and transmission electron microscopic studies. The levels of inflammatory cytokine Tumor necrosis factor(TNF-⍺) was found to be increased in BLM-induced experimental group, whereas, on treatment with daidzein expression of TNF-⍺ was found to be reduced. The results of the present study speculate that daidzein can be used as an agent against BLM-induced pulmonary fibrosis.