Background <p>Pulmonary fibrosis (PF) is a progressive and irreversible interstitial lung disease characterized by excessive extracellular matrix deposition and epithelial–mesenchymal transition (EMT). Increasing evidence indicates that macrophage-derived extracellular vesicles (EVs) are involved in fibrotic remodeling; however, the role of M2 macrophage-derived EV-associated miR-155-5p in PF remains unclear.</p> Methods and results <p>EVs were isolated from M0 and IL-4-induced M2 macrophages and characterized by transmission electron microscopy, nanoparticle tracking analysis, and immunoblotting. Differential miRNA sequencing revealed that miR-155-5p was significantly enriched in M2 macrophage-derived EVs. Fluorescence imaging confirmed the uptake of EVs by MLE-12 cells. Functional analyses demonstrated that M2 EVs promoted EMT in MLE-12 cells, as evidenced by increased expression of Vimentin, α-SMA, Snail, Slug, Twist, and Zeb1, along with decreased E-cadherin expression. Inhibition of miR-155-5p reversed these EMT-associated changes. Luciferase reporter assays and rescue experiments further demonstrated that miR-155-5p directly targeted FOXO3a and SHIP-1. In vivo, bleomycin-induced PF mice treated with M2 macrophage-derived EVs exhibited aggravated pulmonary fibrosis, increased collagen deposition, and enhanced EMT marker expression, whereas treatment with miR-155-5p inhibitor-transfected EVs significantly alleviated fibrotic progression. Moreover, M2 macrophage-derived EVs exhibit favorable biosafety and preferential pulmonary accumulation in vivo.</p> Conclusions <p>M2 macrophage-derived EVs-associated miR-155-5p promotes pulmonary fibrosis progression by enhancing EMT through the FOXO3a/SHIP-1-associated signaling axis. Targeting EV-delivered miR-155-5p may represent a potential therapeutic strategy for pulmonary fibrosis.</p>