In endovascular treatment for cerebral aneurysms using balloons, stents, or flow diverters, a microguidewire or microcatheter needs to be navigated distally across the neck of the aneurysm. However, this is sometimes difficult when there is a wide-neck or large aneurysm with a tortuous or atherosclerotic parent vessel. In this case report, we describe a new technique for navigating a microcatheter into a distal vessel. An 81-year-old woman presented with trigeminal neuralgia and diplopia due to abducens nerve palsy because of a giant cavernous carotid artery aneurysm. We planned stent-assisted coil embolization of the aneurysm and tried to advance a microcatheter into a distal vessel across the neck of the aneurysm. Although we attempted several previously reported techniques, these were unsuccessful. We then navigated a balloon into the aneurysm, slowly inflated it within the aneurysm, pulled it back gently, and sealed the neck orifice of the aneurysm with the balloon. We easily navigated a microcatheter into the distal vessel. The stent-assisted coil embolization was completed with no complications. This novel neck-sealing technique with a balloon for distal access may be useful in cases in which other methods are unsuccessful. In addition, this technique offers the advantages of not producing a loop in the microcatheter within an aneurysm and not requiring retraction of the microcatheter to reduce the loop.