Few procedures in oral surgery show severe complications with the potential to result in life-threatening problems. Subperiosteal orbital abscess is an extremely rare but transcendent complication arising spontaneously or after dental surgery. This report describes a case of subperiosteal abscess of the orbit in a 57-year-old man that occurred following the uneventful extraction of the left maxillary third molar. In the emergency department, proptosis and extraocular muscle dysfunction were marked but no decrease in visual acuity was observed. Echography, computed tomography scan, and magnetic resonance imaging allowed distinction from other types of orbital inflammation. Surgical drainage confirmed the diagnosis. In this patient, orbital abscess was probably caused by extension of the infection to the pterygopalatine and infratemporal regions progressing next to the inferior orbital fissure. This report highlights the difficulty in the clinical diagnosis of this complication.