Frontal sinus mucoceles are benign, pseudocystic lesion deriving from the obliteration of the sinus ostium, resulting in a continuous mucous accumulation. The growing process of a mucocele leads to a progressive enlargement of the sinus cavity, thickening and eroding its bony walls up to invading the surrounding tissues. The surgical procedure through an endoscopic endonasal approach is the current treatment option for such conditions, but in cases with an extensive bone erosion and intracranial or intraorbital extension, a transcranial approach should be preferred. We report a case of a frontal sinus mucocele with unusual intraorbital and intracranial extension, causing exophthalmos and ophthalmoplegia, removed through a transcranial frontal approach and the subsequent obliteration of the sinus.