Silent sinus syndrome is a rarely diagnosed entity. This report adds further insight into the existing knowledge about the etiology and treatment of this clinical condition. We present the case of a 38-year-old female patient, who consulted us because of a painless enophthalmos and hypoglobus, which occurred spontaneously. Clinical and radiographic findings revealed a silent sinus syndrome of the left maxillary sinus and a resultant mild abducens nerve palsy on the left side was suspected after the orthoptic examination. Computed tomography images showed maxillary sinus atelectasis with complete opacification of the left maxillary sinus. Treatment via functional endoscopic sinus surgery restored the left maxillary ostium and the biopsies revealed chronic sinusitis. Thanks to the intact orbital floor and the re-established maxillary ventilation, further operations were not required and the patient underwent follow-up examinations only. The rarity of this condition makes this case an interesting topic.