A significant contributing factor to the progression of late cyanosis in individuals undergoing Kawashima operation is pulmonary arteriovenous malformations. Following the Fontan procedure, arteriovenous malformations may regress. However, in cases with extensive malformations causing severe cyanosis, lobectomy can also be a possible treatment approach. Thereby, we present our two-step treatment strategy in a late Fontan completion complicated by arteriovenous malformations in a Kawashima patient.