Regional Metastatic Melanoma has a relatively high mortality rate. Adjuvant interferon-alpha (IFN-α) has been shown to improve disease-free survival, post-resection. Cardiotoxicity associated with IFN-α use has been described previously in the literature, but here we describe the first case of pericardial effusion with cardiac tamponade secondary to IFN-α 2b treatment of melanoma. Clinicians should be aware of this potentially lethal complication and the possible acuity of its onset.