We describe the tips and tricks of prophylactic intraoperative abdominal aortic aneurysm (AAA) sac embolization during endovascular abdominal aortic aneurysm repair (EVAR) to prevent the occurrence of endoleak and aneurysm sac expansion. We performed prophylactic intraoperative AAA sac embolization for patients with an infrarenal neck angulation > 60° or AAA sac diameter > 60 mm. A 4F catheter was inserted into the AAA sac before EVAR. The aneurysm sac was embolized with n-butyl cyanoacrylate–lipiodol–ethanol (NLE) during proximal neck (PN) aortic balloon occlusion. PN aortic balloon occlusion decreases sac pressure and promotes retrograde blood flow into the sac from aortic branches. PN aortic balloon occlusion can prevent leakage of embolic materials into the aortic branches and allow safe injection of embolic materials into the AAA sac. The endoleak and AAA sac diameter were evaluated by subtraction enhanced MRI at 6 months and yearly after EVAR. It is impossible to identify an endoleak by enhanced CT owing to the presence of a high-density material (Lipiodol or coils) in the aneurysm sac. Intraoperative AAA sac embolization combined with inferior mesenteric artery (IMA) embolization is one of the safe available options. Prophylactic intraoperative AAA sac embolization using NLE during PN aortic balloon occlusion combined with aortic branch embolization is a safe and effective procedure to reduce the incidence of type II endoleaks and prevent sac expansion after EVAR.