An unusual case of infectious mononucleosis complicated by both peritonsillar abscess and postural orthostatic tachycardia syndrome is reported. The patient was diagnosed with Epstein–Barr virus infection early in the disease course by her primary care doctor. She subsequently developed a peritonsillar abscess requiring hospitalisation. Recovery was complicated by the development of postural orthostatic tachycardia syndrome. However, resolution was achieved over the course of approximately 1 year, via conservative measures including graded exercise therapy, without resorting to pharmacotherapy.