Dogs commonly bite porcupines and usually embed multiple quills in the face. Quills that penetrate the eye and the orbit represent a unique diagnostic and therapeutic challenge for the veterinarian since that clinical signs may be unspecific and appear lately in time. This paper describes 3 cases of intra-ocular porcupine quills and discusses the importance of ocular ultrasound to correct diagnosis and management of this affection. Three dogs, all mixed breed, females, one was 4 years old and two were 9 years-old, presented unilateral ocular disorders after biting porcupines and having all facial quills removed. According to the owners, the interval between quills removal and the ocular examination ranged from 20 days to 2 months approximately. Ophthalmic examination showed purulent ocular discharge, blepharospasm, conjunctival hyperemia, chemosis, third eyelid prolapse, deep corneal opacity and neovascularization, buphthalmos and pain. Posterior segment examination wasn't possible due to corneal opacity. In one animal blood cell count was requested, revealing leucocytosis (22.600/mm³). Topical and oral antibiotics and oral anti-inflammatory were administrated. Ocular ultrasound was than performed in all three cases. All three sonographic findings were very similar and showed retinal detachment, important inflammatory/hemorrhagic vitreous process, sub-retinal hemorrhagic process, 2 cases presented cataracts. Two parallel hyperechogenic lines were found in vitreous space extending to posterior wall, representing the porcupine quill of two eyes. In the third case, 2 structures representing the quills were found in the same eye. The ocular bulbus lengths were higher than the contra-lateral eye and ranged from 24 to 26.7 mm. The findings suggested typical endophthalmitis secondary to intra-ocular foreign body. Due to the severity of clinical signs and the lack of response to treatment, enucleation was performed in all dogs. Two eyes were sent to histopathological exam and the quill was found. The microscopic findings were destruction of intraocular tissue, granulomatous reaction with macrophages, neutrophils, lymphocytes and occasional bacteria suggesting endophthalmitis. Porcupine quills are not inert and may carry microorganisms, leading to septic or sterile foreign body reaction. The point of the quill is sharp, which allows penetration of dense tissues. Multiple barbs arranged around the point promote migration of the quill which can penetrate directly the eye and the orbit or indirectly by migration into the orbit from the mouth or periocular tissues. Ocular ultrasound may be helpful to diagnose and locate the quill, and to evaluate the posterior segment, which is important in regard the surgical approach and prognosis.