Epinephrine, the standard treatment for anaphylaxis, is a lifesaving medication that can cause detrimental complications due to wrong-dose or wrong-route errors. Although the known toxicities of epinephrine such as tachycardia, hypertension, and cardiomyopathy are well documented, epinephrine’s paradoxical and prolonged hypotensive effects following overdose are rarely reported. In this case, a 50-year-old man presented to the emergency department with concerns about and symptoms of an allergic reaction. Parenteral epinephrine, antihistamine, and corticosteroid were ordered to manage the suspected anaphylaxis. The patient was inadvertently administered an intravenous push of concentrated epinephrine 1 mg (1 mg/mL) instead of the intended 0.3-mg intramuscular injection, which resulted in clinical manifestations including abnormal electrocardiogram results, elevated cardiac enzymes, and prolonged hypotension that required multiple fluid boluses and continuous infusion to stabilize his blood pressure. Fortunately, the patient responded well to fluid therapy and did not require vasopressors or invasive interventions. Our intention with this case is to add to the limited existing literature on hypotensive effects of epinephrine overdose and increase awareness of the potentially fatal cardiovascular complications. Moreover, we recommend implementing institutional precautionary measures such as stocking epinephrine allergy kits or prefilled epinephrine auto-injectors to help prevent administration errors and ensure patient safety during allergy treatment.