To study the protective effects of ganoderic acid A (GAA) on bleomycin (BLM)-induced pulmonary fibrosis.ICR mice were intratracheally instilled with BLM to induce pulmonary fibrosis on day 0. Then the mice were orally given GAA (25, 50 mg/kg) or dexamethasone (2 mg/kg). After treatment for 21 days, the mice were sacrificed. Wet dry weight (W/D) ratio of lung was used to detect pulmonary edema. Myeloperoxidase (MPO), interleukin-1β (IL-1β), IL-6, tumor necrosis factor-α (TNF-α), malondialdehyde (MDA), and superoxide dismutase (SOD) were detected by enzyme-linked immunosorbent assay. Hematoxylin and eosin staining was used to evaluate the pathological changes. The levels of transforming growth factor β (TGF-β), phosphorylated-smad3 (p-smad3), p-IκB, and p-nuclear factor-kappa B (NF-κB) in lung tissue were detected by western blot.GAA treatment significantly improved MPO activity, W/D ratio, and lung histopathology. The protective effect of GAA may be related to downregulation of TNF-α, IL-1β, IL-6, MDA and upregulation of SOD. In addition, GAA significantly decreased the levels of TGF-β, p-smad3, p-IκB, and p-NF-κB, compared with those in BLM group.GAA has protective effect on BLM-induced lung injury, and TGF-β/Smad-3/NF-κB signaling pathway may play an important role in the pathogenesis of BLM-induced lung injury.