Peritonsillar abscess is the most common infection of the deep tissues of the head and neck and occurs mainly as a complication of streptococcal angina, but it may also be caused by other bacteria, such as Fusobacterium necrophorum or Streptococcus anginosus streptococci. The default treatment in a patient with a peritonsillar abscess includes drainage, antibiotic therapy and symptomatic treatment. Thanks to this treatment, most patients do not develop further complications. In untreated people or when treatment is introduced too late, the infection may have a complicated course and spread towards deeper tissues. In this study, we present a case of a patient with a complicated course of peritonsillar abscess caused by Streptococcus anginosus bacteria.