Odontogenic infections are one of the most common dental problems, which affect 80%u90% of the population. Untreated odontogenic infections can cause life-threatening complications such as necrotizing fasciitis, descending necrotizing mediastinitis, internal jugular vein thrombosis, cavernous sinus thrombosis, carotid artery pseudoaneurysm or rupture, and systemic inflammatory response syndrome. This report aims to present a mediastinitis case, in a 22-year-old healthy male patient, which originated from an odontogenic infection. The patient was hospitalized because of worsening general health status, despite the antibiotherapy. Computed tomography (CT) scan revealed that periapical abscess was spreading to the mediastinum through retropharyngeal space. The patient was successfully treated by IV antibiotherapy, transcervical drainage, and extraction of tooth.