Objective: Case report of posterior communicating artery aneurysm (ACoP) related unilateral oculomotor nerve palsy (ONP). Introduction: The ACoP aneurysms represents the 25% of all aneurysms. It could cause ONP because of his close relation of the aneurysm and the oculomotor nerve. The treatment in symptomatic patients should be the exclusion of the aneurysm. Case report: 38-year-old woman with headache of 15 days of evolution and acute ONP. CT angiography shows a 3x7 mm ACoP aneurysm. Microsurgery and clipping were considered the best treatment and were realized without complications. The patient evolves with complete recovery of his ONP with complete exclusion of the aneurysm. Discussion: ACoP aneurysm should be considered in ONP working diagnosis. The treatment is exclusion of the aneurism either by endovascular or microsurgical techniques. Microsurgical clipping has shown better functional outcomes than endovascular therapy.