Life-threatening cervical complications associated with infectious mononucleosis are rare. The combination of acute epiglottitis and subsequent necrotizing fasciitis of the head and neck in a patient with infectious mononucleosis has not been reported to date.A 47-year-old female with infectious mononucleosis and epiglottitis was admitted to hospital for i.v. therapy. Owing to her poor clinical condition and the spread of the infection to the throat and superior mediastinum, as evidenced by CT, a cervical debridement was performed. After cervical debridement, histological findings were consistent with necrotizing fasciitis. The bacteria identified were Streptococcus viridans, Veilonella spp. and Capnocytophaga spp. The patient was hospitalized for 33 days.Mononucleosis, usually a benign condition, may be associated with life-threatening septic complications in the neck and chest. Serial CT or MRI scans are necessary to assess the development of the infection in the deep layers of the neck. Rapid medical treatment, extensive surgical debridement and intensive care are vital.