Isolated sphenoid sinus fungus ball is a very rare condition. CT is the most used imaging investigation for diagnosis. In some cases, MRI may provide further information to evaluate the extracompartmental invasion. We report the case of an elderly female patient who presented with headache and a soft tissue mass filling the right sphenoid sinus on CT, misdiagnosed as simple sinusitis. After 1 year, with recrudescence of symptoms, brain MRI showed a hyperintense soft tissue mass on T 1 weighted images within the right sphenoidal sinus; a new CT examination revealed calcifications within the mass. Surgical histological examination showed fungus ball. Fungal ball should be included in the differential diagnosis of T 1 hyperintense lesions in the sphenoid sinus.