A 71-year-old man developed general fatigue, appetite loss, and headache. Two months later, he noticed diplopia. Examination demonstrated reduced visual acuity and complete ophthalmoplegia of the left eye. Brain MRI disclosed a mass that extended from bilateral cavernous sinus to the clivus. There were left cervical lymphadenopathy and a right abdominal mass. A needle biopsy of the abdominal mass revealed non-Hodgkin lymphoma. Although malignant lymphoma at the cavernous sinus is not common, it should be an important consideration in the differential diagnosis of mass at the cavernous sinus.