Background <p>Primary orbital adenoid cystic carcinoma (ACC) not arising from the lacrimal gland is very rare with few previous case reports either involving the orbital apex, medial orbit or inferior orbit. There is only one previous case report of primary adenoid cystic carcinoma involving the inferior orbit. The aim of this case report was to present a rare instance of primary adenoid cystic carcinoma (ACC) arising in the inferior orbit without lacrimal gland involvement, uniquely associated with skull base and cranial nerve infiltration, and to emphasize the importance of imaging and histopathological evaluation in early diagnosis and management of uncommon orbital tumors.</p> Case presentation <p>Our case is a 65-year-old male presented with progressive ophthalmoplegia. Clinical examination revealed minimal left proptosis. MRI demonstrated an ill-defined inferior orbital mass, extending through the pterygopalatine fossa along the maxillary, vidian, and infraorbital nerves. The lacrimal gland was not involved. CT imaging showed skull base infiltration of the pterygoid process. Biopsy confirmed primary adenoid cystic carcinoma with basaloid and tubular histological patterns. No distant metastasis was identified on systemic staging. The patient received palliative chemoradiotherapy, with subsequent imaging showing partial tumor regression.</p> Conclusion <p>This is the second documented case of primary inferior orbital ACC and the first with concurrent skull base and cranial nerve infiltration without lacrimal gland involvement. Early recognition and accurate imaging by combined MRI with contrast and CT is required for early detection of both perineural spread (PNS) and skull base invasion with consequent early management.</p>