Spontaneous rupture and subsequent bile peritonitis are rare complications of choledochal cysts. Of these complications, the formation of a biliary pseudocyst is an unusual form, and its preoperative diagnosis is difficult. In this report, we describe 2 cases showing spontaneous rupture with biliary pseudocyst formation. Inflammatory tissue surrounded those pseudocysts, one of which was adjacent to the perforation and the other formed in the transverse mesocolon apart from the biliary tract. These pseudocysts were removed by careful dissection, and single-stage cyst excision with biliary reconstruction was successfully performed in both cases.