Lung fibrosis, including idiopathic pulmonary fibrosis, is an intractable disease accompanied by an irreversible dysfunction in the respiratory system. Its pathogenesis involves the transforming growth factorβ (TGFβ)-induced overproduction of the extracellular matrix from fibroblasts; however, limited countermeasures have been established. In this study, we identified osa-miR172d-5p, a plant-derived microRNA (miR), as a potent anti-fibrotic miR. In silico analysis followed by an in vitro assay based on human lung fibroblasts demonstrated that osa-miR172d-5p suppressed the gene expression of TGF-β activated kinase 1 (MAP3K7) binding protein 1 (Tab1). It also suppressed the TGFβ-induced fibrotic gene expression in human lung fibroblasts. To assess the anti-fibrotic effect of osa-miR172d-5p, we established bleomycin-induced lung fibrosis models to demonstrate that osa-miR172d-5p ameliorated lung fibrosis. Moreover, it suppressed Tab1 expression in the lung tissues of bleomycin-treated mice. In conclusion, osa-miR172d-5p could be a potent candidate for the treatment of lung fibrosis, including idiopathic pulmonary fibrosis.