There are few reports of acute myocardial infarction (AMI) relating to the occlusion of the conus branch, most of which are iatrogenic in nature. So far as we are concerned, this is the first case of spontaneous AMI with isolated conus branch occlusion. Electrocardiogram (ECG) showed mild elevation of ST segment in leads V(1) through V(3). Cardiac makers of myocardial infarction were positive. Right coronary angiography revealed an isolated occlusion of the conus branch. Penetration of the guidewire in the occluded lesion was attempted, and recanalization was successfully achieved. The patient was discharged without any adverse events.