Carbon monoxide (CO) poisoning is a toxicological emergency and may be responsible for more than half of all fatal poisonings worldwide. Serious effects of CO are frequently seen in the brain and heart as well as other organs that are particularly sensitive to hypoxia. Cardiac manifestations include dysrhythmias, myocardial infarction, and even cardiac arrest. Even in mild cases of CO poisoning with absent chest pain, the emergency physician should evaluate features of myocardial injury, as this can serve as a predictor of mortality and morbidity. A case of a young, healthy man with severe CO poisoning presented with atrial fibrillation (AF) and vasospastic angina, and he was managed successfully with high-flow oxygen.