To our knowledge, acute myocardial infarction after jellyfish envenomation has not been reported previously. We describe a previously healthy 45-year-old male diver who had an acute inferior myocardial infarction with right ventricular involvement after a jellyfish sting on his left forearm while diving in the Gulf Sea. The patient had a normal controlled ascent after the incident. He had no risk factors for coronary artery disease, and cardiac catheterization revealed normal coronary arteries. Acute myocardial infarction should be considered in patients who experience chest pain or have hemodynamic compromise after jellyfish envenomation.