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Introduction: pulmonary fibrosis (PF) is a chronic and progressive disease with a median survival of 3–5 years following diagnosis. It can be conceptualized as resulting from an imbalance between normal processes of synthesis and degradation of extracellular matrix(ECM) components. Matrix Metalloproteinases (MMPs) in particular MMP-2, a member of proteolytic enzyme family, degrade the extra cellular matrix and basement membrane and have an important role in the development of pulmonary fibrosis. In this research, the expression of MMP-2 protein in the pulmonary fibrosis induced by bleomycin was investigated in the form of qualitative and quantitative in mice. Materials & Methods: In this experimental study, sixteen C57BL/6 mice were divided into 2 groups. Mice received in group1(Experiment group), bleomycin sulfate and in Group2(control group) CMC intraperitoneally. The mice were sacrificed at the end of experiment and Lung samples were collected from two groups and were prepared for histological and immunohistochemical studies. Then investigated the histological changes of lung tissues and MMP-2 protein expression and Results were analyzed using Student t-test. Findings: Histological studies in the experimental group showed inflammatory response, collagen deposition and increase of connective tissues amount in the lung alveolar septa in comparison to control group. Immunohistochemical studies showed that the number of MMP-2 protein expressing cells significantly increased in the experimental group compared to the control group(P<.001). Discussion & Conclusion: The results of this study showed that the number of cells expressing MMP-2 protein increases in pulmonary fibrosis induced by bleomycin.