Recently, intraoperative fluorescence video angiography using indocyanine green (ICG) has been widely used in aneurysm surgery. This is a simple and useful method to confirm complete occlusion of the aneurysm lumen and preservation of blood flow in the arteries around the aneurysm. However, the observation field of ICG video angiography is limited under a microscope, making it difficult to confirm the flow in the arteries behind the parent arteries or aneurysm. The authors developed a new technique of intraoperative endoscopic ICG video angiography to assess the blood flow in perforating arteries hidden by the parent arteries or aneurysm. The endoscope emits excitation light with a wavelength of approximately 800 nm, and video images were obtained through a cut filter. The authors used this ICG fluorescence endoscope in treating 3 patients with unruptured cerebral aneurysms. During clip placement, the endoscope was inserted to confirm aneurysm occlusion. Then, ICG was intravenously administered, and the fluorescence in the vessels was observed via the endoscope as well as under the microscope. The blood flow in the perforating arteries was clearly identified, and no procedural complication occurred. The authors conclude that the technique is very useful and facilitates intraoperative real-time assessment of the patency of perforating arteries behind parent arteries or aneurysms.