Primary biliary cirrhosis (PBC) is an autoimmune chronic liver disease with worldwide increasing morbidity. However, the etiology of PBC is still unclear. Recently, the epithelial-mesenchymal transition (EMT) and interleukin-17A (IL-17A), a pro-inflammatory cytokine, were proposed to be involved in the pathogenesis of PBC. Therefore, in this study, we aimed to clarify the roles of IL-17A and/or EMT in the onset of PBC. The results showed that the median serum IL-17A level was significantly higher in 29 PBC patients (average course of 40.69 months) than that of 11 healthy controls. The intrahepatic biliary epithelial cells (IBECs), the major target of destruction in PBC, underwent EMT in PBC patients. The immunohistochemical analysis revealed that the protein levels of IL-17A receptor were increased in IBECs and the IL-17A protein was accumulated around the IBECs in the PBC patients. These results imply that the IL-17A-mediated signaling and EMT of intrahepatic biliary epithelial cells (IBEC-EMT) are key pathogenic processes of PBC. To study the association between IL-17A and IBECs-EMT, we then examined if IL-17A induced EMT using a human cell line of IBECs (HIBECs). After the treatment with IL-17A for 48 h, HIBECs changed into bipolar cells with a fibroblastic morphology. Additionally, the results of real-time PCR and Western blot analyses demonstrated that IL-17A up-regulated the expression of a mesenchymal marker vimentin and down-regulated the expression of an epithelial marker E-cadherin in HIBECs in the dose- and time-dependent manners. These results suggest that IL-17A may play an important role in the IBECs-EMT.