Background: Immunoglobulin (Ig) G4 associated sclerosing cholangitis is a rare inflammatory disease of the biliary tract. Although it is a very progressive condition, it responds to steroid therapy. IgG4 associated sclerosing cholangitis can mimic pancreatic carcinoma, cholangiocarcinoma, and primary sclerosing cholangitis; therefore, it is very important to obtain a differential diagnosis. IgG4 sclerosing cholangitis is a biliary form of IgG4 related systemic disease, in which afflictions of more organs is afflictions of more organs are common, typically biliary form together with pancreatic one. Nonspecific symptoms are obstructive icterus, fatigue, and weight loss. Atypical imaging of the biliary tree and pancreas can be used to distinguish it from other diseases. Laboratory data show elevation of bilirubin, liver enzymes, IgG4 and total IgG concentrations. Sometimes IgE is also elevated with the eosinophilia, oncomarker CA 19-9 and autoimmune antibody is sometimes detected. Case: This article presents a case of IgG4 sclerosing cholangitis and its related findings. The patient was intially referred for suspected pancreatic tumour, the presumed diagnosis was later changed to cholangiocarcinoma type 4 with concurrent autoimmune pancreatitis. Atypical imaging in cholangiography made us suspect IgG4 inflammation and the diagnostic process began. Conclusion: The diagnosis of this disease uses so called HISORt criteria. It is a very complex process in which the success of steroid therapy as a final step can be conclusive, as it was in our case. It is essential to exclude a malign neoplastic growth.