Group A Streptococcus is well established as the most common pathogen causing necrotizing fasciitis. In contrast, Group B Streptococcus (GBS, or Streptococcus agalactiae) is a rare cause of necrotizing fasciitis, particularly in adults. We present the case of a patient who developed a fulminant case of GBS necrotizing fasciitis on a backdrop of a previously undiagnosed malignancy, and review the relevant literature.