Acute pharyngitis is commonly encountered, but a definite etiological diagnosis is difficult. Although co-infection with Group A Streptococci (GAS) and Epstein-Barr virus (EBV) is uncommon, general physicians should consider the possibility of EBV co-infection in patients with GAS pharyngitis who fail to show prompt remission of symptoms following appropriate antibiotic treatment. In this article, we present a rare case of a 16-year-old girl who had co-infection with GAS and EBV. She developed acute glomerulonephritis and left ventricular dysfunction in an overlapping manner. We were able to follow her until she healed, and herein describe the pathogenesis of her systemic and pulmonary edema.