The efficacy and the adverse effects of intravenous iron formulas have been well established. However, there are few reports of anaphylaxis of ferric carboxymaltose (FCM). A man received intravenous FCM for the treatment of restless legs syndrome. The FCM gave rise to angioedema, urticaria, chest tightness, sinus tachycardia, and hypotension. In the end, epinephrine and dexamethasone resolved the symptoms. The findings were consistent with anaphylactic hypersensitivity reaction from FCM. We need to be careful when we administer FCM in clinics.