Invasive lung myofibroblasts are the main cause of tissue remodeling in idiopathic pulmonary fibrosis (IPF). A key mechanism contributing to this important feature is aberrant crosstalk between the abnormal/injured lung epithelium and pulmonary fibroblasts. Here, we demonstrated that lungs from patients with IPF and from mice with bleomycin (BLM)-induced pulmonary fibrosis (PF) are characterized by the induction of human epididymis protein 4 (HE4) overexpression in epithelial cells. HE4 knockdown primarily in epithelial cells attenuated BLM-induced PF in mice, whereas the administration of recombinant mouse HE4 exacerbated fibrosis after BLM stimulation. Mechanistic analysis showed that HE4 and annexin II (ANXA2) specific binding enhanced the profibrotic phenotype in epithelial cells, and directly promoted lung fibroblast activation, leading to aberrant epithelial-fibroblast crosstalk and the persistent myofibroblast phenotype. The HE4 and ANXA2 binding site was located after the 30th amino acid at the N terminus of the HE4 molecule. Finally, intratracheal administration of HE4 shRNA lentivirus protected mice against BLM-induced PF. These data suggest that HE4 can serve as a novel therapeutic target in the treatment of IPF.