The anterior cerebral artery A1 segment aplasia is an anatomical variation of the Willis circle. It is very rare and mostly associated with the anterior communicating artery aneurysm, but this relationship has still not been thoughtfully explored. The hemodynamic factors are speculated to be the main pathophysiological mechanism of the aneurysm formation. The risk of the aneurysm rupture in the setting of A1 aplasia is not well elucidated. Endovascular treatment may have good outcome in short term. Long term studies are needed to evaluate the recurrence and recanalization rate. Here, we describe a case of unilateral anterior cerebral artery A1 segment aplasia associated with a ruptured anterior communicating artery aneurysm in which the endovascular embolization was successful performed without any complication.