We report a rare casse of optic nerve involvement as the first sign of systemic sarcoidosis. A 43-year-old white woman presented with visual loss in her right eye, and the clinical appearance of optic nerve head swelling. Visual acuity was reduced to 20/200, and the only clinical signs were the presence of an enlarged optic nerve head, with engorged retinal veins and flame-shaped haemorrhages. Computed tomography scans showed an enlarged orbital portion of the right optic nerve, which was confirmed by magnetic resonance imaging. With a diagnosis of optic nerve tumour (possibly glioma) a surgical resection of the tumour was performed. Histopathology showed multiple nodular granulomas with epithelioid cells, consisted with the diagnosis of sarcoidosis. This was confirmed by systemic involvement of the parotids and liver. We review the literature and consider all possible involvement of the optic nerve in sarcoidosis. The rarity of systemic sarcoidosis with a first manifestation as papilloedema is discussed.