A 43-year-old lady with type 2 diabetes mellitus and bronchial asthma presented with varicella zoster infection, dyspnea, and neck fullness. An urgent computed tomography scan revealed a mediastinal abscess with superior vena cava thrombus. Blood, mediastinal pus, and swab from a vesiculopustule on the neck cultured group A beta hemolytic Streptococcus. She recovered with a combination of broad spectrum antimicrobials, antivirals, and surgical drainage. This case illustrates the rare occurrence of mediastinal abscess and acute superior vena cava obstruction caused by group A beta hemolytic Streptococcus complicating adult varicella zoster.