Coronary arterial complications associated with Kawasaki disease (KD), such as a giant coronary aneurysm, determine the relative risk of future cardiac events and require lifelong medical treatment. Here, we describe a 24-year-old man who developed myocardial infarction due to poor adherence to medical treatment for a giant coronary aneurysm in the chronic phase of KD. He was hospitalized two hours after the onset of chest pain. The presence of the giant coronary aneurysm made primary percutaneous coronary intervention (PCI) difficult. However, we were able to perform primary PCI successfully utilizing previous coronary computed tomography (CT) angiographic pictures as a reference. This case provides valuable insight for the management of coronary arterial complications associated with KD. Patients in the chronic phase of KD are usually asymptomatic, even in the presence of giant coronary aneurysms which have been reported to have a high risk of morbidity and mortality. Therefore, patient education is critical for preventing poor adherence to medical treatment for coronary arterial complications. In preparation for potential coronary intervention in the future, it is also useful to perform coronary CT angiography, coronary magnetic resonance (MR) angiography, and/or coronary angiography on a regular basis while patients remain free from serious cardiac events.