Introduction <p>Lung cancer is a highly prevalent and deadly disease worldwide, causing over 1.2 million deaths each year. Pingxiao Pian (PXP) tablets, a Chinese traditional medicine, have been widely applied in the treatment of lung cancer. However, the mechanism underlying therapeutic effects of PXP tablets remains undisclosed.</p> Methods <p>A549 human LUAD cell line was utilized for in vitro experiments. Transfection of miR-29b mimic was performed using Lipofectamine 3000. PXP was purchased and dissolved into PBS and drinking water after carefully removing the outer coating. Dual-luciferase reporter assay was conducted to assess the regulatory effect of miR-29b on TGF-β1. The protein levels of epithelial-mesenchymal transition (EMT) markers and activation of TGF-β1 pathway were characterized using immunoblotting analysis.</p> Results <p>PXP reduced the invasiveness and proliferation of LUAD cells by increasing miR-29b-3p expression in vitro. Overexpression of miR-29b-3p resulted in decreased cell proliferation and invasiveness, while silencing of miR-29b-3p in the A549 cells displayed the opposite effect. Moreover, PXP treatment reversed the increased cell proliferating rate triggered by miR-29b-3p silencing. Additionally, PXP was found to hamper EMT occurrence in A549 cells by regulating miR-29b-3p and reduce expression of N-cad and vimentin. Overexpression of miR-29b-3p blocked the phosphorylation of Smad2/3 and decreased TGF-β1 expression. Luciferase assay results indicated that miR-29b-3p directly regulated TGF-β1 expression. In vivo tumor formation experiments confirmed the tumor-reducing effects of PXP and the role of miR-29b in tumor progression. PXP treatment decreased tumor size and weight via regulating miR-29b-3p.</p> Conclusion <p>Our study suggests that PXP exerts anti-tumor effects in LUAD through the regulation of miR-29b and the inhibition of EMT via the TGF-β1/Smad2/3 pathway.</p>