A 30-year-old male suffered an orbital trauma due to a traffic accident. At the Emergency Unit, the patient presented with avulsion of the upper left eyelid in the medial canthus, wounds in the lower eyelid and the inferior canaliculus, conjunctival laceration, proptosis and palpebral hematomas. The patient reported persistent diplopia. During the examination, exotropia and total absence of adduction were observed. Computerized tomography (CT) revealed a discontinuity at the left medial rectus. No orbital fractures were identifiable. The medial rectus was still attached to its anatomic insertion at the globe. The discontinuity was suggestive of laceration or rupture of this muscle at approximately 10-12 mm from its insertion. Surgical exploration revealed total rupture of the medial rectus at approximately 12 mm from its insertion. The posterior edge of the damaged muscle was found and sutured to its anterior edge with 6-0 polyglactin. The following day, the eyes were completely straight and the patient did not mention any signs of diplopia. Botulinum toxin injection into the ipsilateral lateral rectus was not necessary. After six months of follow-up, the patient still reported no diplopia. When muscular laceration is suspected after an orbital trauma, early CT is recommended. The only procedures that assure a significant recovery of the normal function of the eye are early muscle repair and avoidance, if possible, of transposition surgery.