Mirizzi syndrome is a rare complication of gallstone disease, and results in partial obstruction of the common bile duct or a cholecystobiliary fistula. Moreover, congenital anatomical variants of the cystic duct are common, occurring in 18%-23% of cases, but Mirizzi syndrome underlying an anomalous cystic duct is an important clinical consideration. Here, we present an unusual case of type Ⅰ Mirizzi syndrome with an uncommon anomalous cystic duct, namely, a low lateral insertion of the cystic duct with a common sheath of cystic duct and common bile duct.