Oxidative stress is caused by the imbalance between the production of reactive oxygen species and the body's ability to detoxify them or repair the resulting damage. Current evidence suggests that acute lung injury can lead to pulmonary fibrosis.Pulmonary fibrosis is a progressive and fatal interstitial pneumonitis with high mortality and limited successful treatment. The present study was designed to assess the protective effect of thymoquinone (TQ) and whether it can attenuate the severity of oxidative stress and inflammatory response during bleomycin (BLM) induced pulmonary fibrosis. Male albino rats were treated with either BLM and/orTQ. BLM significantly increased the levels of Lactate dehydrogenase (LDH), total protein and mucin in bronchoalveolar lavage fluid (BALF) and these effects were significantly ameliorated by TQ treatment. BLM also caused a significant elevation in the levels of lipid peroxides and nitric oxide (NO) accompanied with a significant decrease in the antioxidant enzyme activity of superoxide dismutase (SOD). TQ treatment restored these markers toward normal values. Moreover, histopathological examination confirmed the protective effect of TQ.