Recent progress in diagnostic imaging techniques, such as MRI and CT, has shown that Rathke's cleft cyst is more common than once thought. However, few cases have been reported in which a cerebral arterial aneurysm was merged with a symptomatic Rathke's cleft cyst. We present a case of bilateral internal carotid aneurysms associated with a symptomatic giant Rathke's cleft cyst. A 66-year-old-woman with a visual disturbance was admitted to our hospital. CT and MRI showed a large mass in the frontal base to the suprasellar region. The mass showed isosignal intensity in T1-weighted images (WI), a ringed enhancement with Gd-DTPA, and hyperintensity in T2WI. An angiography showed bilateral A1 elevation but no tumor stain. In addition, unruptured aneurysms appeared in the inside back C2 portion of the bilateral internal carotid arteries. For these lesions, a bifrontal craniotomy was performed. In a single operative approach, the mass lesion was removed and the aneurysms were successfully clipped. The aneurysms adhered strongly to the wall of the mass. The histological diagnosis of the mass was Rathke's cleft cyst. A precise pre-operative understanding of the anatomical structure and a careful operative procedure are important for the treatment of these complex lesions.