Two cases of coronary aneurysm developed in the late period after Kawasaki disease (KD). Case 1 involved a 13-year-old boy who had aneurysms develop after a diagnosis of complete regression. Case 2 involved a 29-year-old man who had a new aneurysm develop after he was older than 20 years. Physicians need to be aware that coronary aneurysms can develop in patients with antecedent KD even after regression or in adulthood.