Protamine sulfate is considered a "life-saving" antidote for heparinized patients with major bleeds. Although the beneficial attributes and application of protamine sulfate in various clinical settings cannot be argued, it also has an impressive side-effect profile. Kounis syndrome (KS) is an acute coronary syndrome in the setting of an allergic reaction, which can be induced by numerous allergens. Herein, we report a case of KS secondary to the use of protamine sulfate after cryoablation for atrial fibrillation.