We report a case of Tolosa-Hunt syndrome (THS) in a patient with systemic lupus erythematosus studied with MRI. Magnetic resonance showed enlargement of the cavernous sinus and compression of the carotid syphon by enhancing tissue. In particular, fat-suppressed T1-weighted images before and after contrast agent injection and MR angiography showed extension of the abnormal tissue to the apex of the orbit and narrowing of the internal carotid artery. A presumptive diagnosis of THS was made and steroid treatment was started with rapid relief of symptoms. Follow-up MR study after steroid therapy demonstrated sub-total resolution of the neuroradiological findings. Neuroradiological findings in THS are quite typical but they may be subtle; furthermore, the presence of a systemic disease may suggest secondary involvement of the cavernous sinus. Utilization of the appropriate MR techniques and follow-up exams may contribute to the diagnosis of THS even in the presence of other systemic diseases.