The authors report an interesting case with a ruptured internal carotid artery aneurysm that presented as a sellar haematoma mimicking radiologically a pituitary adenoma, and clinically a pituitary apoplexy. A 53-year-old woman presented with a 2-week history of episodic severe headache and vomiting associated, 3 days prior to admission, with left ophthalmoparesis and transient right hemiparesis. Brain MRI showed a large intra- and suprasellar mass suggestive of a pituitary macroadenoma. Hormonal profiles showed hyperprolactinaemia and subsequent cerebral angiography demonstrated a carotid cavernous aneurysm. The patient underwent surgery via a subfrontal approach to manage both lesions. At operation, the suspected pituitary adenoma was revealed to be a sellar haematoma; the aneurysm was successfully clipped. Postoperatively, the patient developed hypotension and right hemiparesis which, as well as the third nerve paresis, progressively improved to full recovery. At 12 months follow-up the patient is neurologically intact and generally well. The clinical features, the management of such a case and the importance of differential diagnosis in the acute stage are emphasised and discussed along with relevant literature.