Background and Purpose: Endovascular treatment of unruptured posterior circulation intracranial aneurysms (UPCIAs) is limited in the International Study of Unruptured Intracranial Aneurysms (ISUIA). The aim of this study is to evaluate the periprocedural morbidity, mortality, and midterm clinical and angiographic follow-ups of endovascular treatment of UPCIAs. Materials and Methods: Retrospective analysis of all patients treated in a 2-year period (89 patients: 10-78 years of age, mean: 45.5 +/- 14.3/92 UPCIAs). Fifty-eight aneurysms were found incidentally, 12 in association with mass effect symptoms and 22 with stroke. Results: A clinical improvement or stable outcome was achieved in 84 patients (94.4%). The two cases of permanent morbidity included a patient with paralysis and another patient with hemianopia. One patient died after treatment of a giant fusiform vertebrobasilar aneurysm. In one patient, the aneurysm ruptured during treatment, resulting in death. Another patient suffered a fatal aneurysm rupture 4 days after treatment. Giant size (P = 0.005) and mass effect presentation (P = 0.029) were independent predictors of unfavorable outcomes in UPCIAs. Angiographic follow-up was available in 76 of the 86 surviving patients (88.4%) with a mean of 6.8 months (range: 1-36 months). Recanalization in six patients (7.9%) at 3 months, 4 months, 4 months, 24 months, and 36 months required retreatment in three patients. In-stent stenosis of >50% was found in three patients. Conclusion: Endovascular therapy is an attractive option for UPCIAs with stable midterm outcome. However, the current endovascular option seems to have a limitation for the treatment of the aneurysm with giant size or mass effect presentation.