A case of spontaneous haemorrhage into the retropharyngeal and parapharyngeal space secondary to bleeding from a thyroid cyst is described. While many conditions are known to cause this entity, no previous papers have reported a thyroid cyst to cause such extensive haemorrhage. Haemorrhage in these spaces is of particular importance as it causes rapid airway compromise and can be life-threatening. Forty cases of non-traumatic retropharyngeal and parapharyngeal haematomas have been reported in the literature to date. Although the diagnosis can be easily established in most patients, no published review of this condition exists. This paper reviews all reports of non-traumatic retropharyngeal and parapharyngeal haematoma published in the literature to date and discusses management guidelines. We also present here for the first time the demographics and treatment results of this rare entity.