Parvovirus B19 (PVB19) and Epstein-Barr virus (EBV) commonly cause infection worldwide, with most persons infected during childhood. Their disease courses are usually mild and brief; however, PVB19 and EBV have been implicated as etiologies of viral myocarditis. We report a case of PVB19 and EBV coinfection associated with fulminant lymphocytic myocarditis. We address the implications of the case, including the differential diagnosis, immunomodulatory treatment considerations, and evidence for the pathologic roles of PVB19, EBV, and coinfection in myocarditis. Although the pathogenic roles of PVB19 or EBV alone in myocarditis are not well established, coinfection of PVB19 and EBV may unlock their pathogenic roles causing fulminant myocarditis. Treatment with steroids and intravenous immunoglobulin G in a patient with rapid clinical deterioration despite the presence of active infection on endomyocardial biopsy by polymerase chain reaction can result in a safe and quick recovery of fulminant viral myocarditis. Early and aggressive intervention, including both mechanical circulatory support and immunomodulatory therapy, may be key to improved outcomes in cases of fulminant myocarditis.