Emergency physicians should be aware of adverse drug reactions prior to administering medication. Alteplase, or tissue plasminogen activator (tPA), is a common medication in the emergency department, whether it is being used for a stroke or pulmonary embolus. Angioedema can be caused by almost any medication. tPA administration can cause an atypical form of angioedema. The following case was one of unilateral orolingual angioedema associated with tPA administration in the emergency department in a stroke patient. The mechanism of tPA-induced angioedema is poorly understood. Angioedema can be treated with stopping the infusion of medication, Benadryl® (Johnson & Johnson Consumer, Inc., Fort Washington, PA), histamine antagonists, steroids, and epinephrine. Angioedema is a life-threatening event in certain situations, and emergency medicine providers would do well knowing how to approach these cases.