We herein report a case of a 56-year-old man with IgG4-related sclerosing cholangitis (IgG4-SC) with no biliary stricture, but with a severely thickened bile duct wall. Contrast-enhanced computed tomography showed diffuse swelling of the pancreas and thickening of the common bile duct (CBD) wall with delayed enhancement. Obvious diffuse wall thickening of the CBD was observed on endoscopic ultrasonography. However, endoscopic retrograde cholangiography showed no biliary stricture in the CBD that had thickened. Although IgG4-SC has been classified by a stenotic lesion on cholangiography, we should be aware of some IgG4-SC cases showing only bile duct wall thickness without any biliary stricture.