A 78-year-old man with mild coronary arteriosclerosis on coronary CT angiography underwent MRI of the prostate with the administration of GBCA (gadopentetate dimeglumine). He developed acute coronary syndrome immediately after the intravenous injection of GBCA, and recovered after the administration of nitroglycerine, atropine sulfate, and hydrocortisone. He was discharged on the ninth day of hospitalization without recurrent chest symptoms. This is the second reported case of Kounis syndrome caused by GBCA. Kounis syndrome caused by MRI contrast media is rare, but we should recognize that all contrast agents have the potential to cause Kounis syndrome.