Here, we found mesencephalic astrocyte-derived neurotrophic factor (MANF), a hepatic protector, was upregulated in human ICC tissues and sleeping beauty transposon (SBT) or thioacetamide (TAA)-induced mice ICC tissues. We verified the oncogenic role of MANF in ICC using cell lines overexpressing/knocked down MANF and mice specifically knocked in/out MANF in hepatocytes. Lineage tracing revealed that MANF promoted mature hepatocytes transformation into ICC. Mechanistically, we found a complex composed of MANF, CK19, and Notch2 intracellular domain (NICD2). MANF interacted with CK19 at Ser35 to suppress CK19 phosphorylation and membrane recruitment. Cytosolic CK19 bound to AR domain of NICD2 to stabilize NICD2 protein level and trigger Notch signaling, which contributed to hepatocytes transformation to ICC. We uncover a novel role of MANF and the original mechanism，which shed light on ICC intervention and treatment.