Non-traumatic mediastinal abscesses are very rare in children; we can classify them into 2 types: descending mediastinitis (or mediastinitis by extension or by contiguity) complicating an otorhinolaryngological or esophageal etiology and mediastinitis generated by direct blood inoculation in a context of a septicemia or primary mediastinitis which is exceptional. We describe a case of right pleuropulmonary staphylococcal disease with bilateral mediastinal localization in a previously healthy 9-month-old infant. It was revealed by sepsis with severe respiratory distress. The germ was isolated from the pleural puncture fluid. A thoracic computed tomography was indicated due to a widening mediastinum noted on chest X-ray in addition to pleuropulmonary involvement. Thoracic computed tomography revealed a huge bilateral mediastinal abscess which was curbed thanks to right pleural drainage with adapted antibiotic therapy. Other investigations did not show any immune abnormalities in this infant. Mediastinitis represents a diagnostic and therapeutic emergency; those that are secondary to direct blood or lymphatic dissemination even very rare; should be considered in any context of severe sepsis including staphylococcus or streptococcus pneumonia. Since 1985 only 11 cases of such mediastinal abscesses have been reported.