This study was conducted to determine the risk factors and the clinical impact of intraprocedural aneurysm rupture (IAR) and periprocedural ischemia in the treatment of symptomatic and asymptomatic unruptured intracranial aneurysms (UIAs). A single-center retrospective data analysis of 563 UIAs treated between 2000 and 2010 was conducted. Treatment assignment was made on the basis of individual aneurysmal criteria in an interdisciplinary neurovascular conference with attending neurosurgeons, neuroradiologists and neurologists. In 363 microsurgical and 200 endovascular procedures, the permanent morbidity rate was 4.9 and 6 %. The overall mortality rate was 0.7 %-no procedure-related death occurred in microsurgery, and four patients had fatal outcomes after endovascular treatment. IAR occurred in 34 (9.4 %) microsurgical and 8 (4 %) endovascular procedures (p = 0.03). Risk factors for IAR were age, aneurysm diameter, symptomatic aneurysms, hypertension and smoking in microsurgery. IAR was associated with significantly worse outcome at discharge after microsurgical and at discharge and follow-up after endovascular procedures and was followed by fatal outcome in four endovascular cases. Periprocedural ischemia (12.1 vs. 9 %) resulted in significantly worse outcome in both groups. Risk factors for periprocedural ischemia were IAR during microsurgery, aneurysm diameter, symptomatic aneurysms and smoking in either group. Treatment of UIAs can be conducted with an equivalent low rate of permanent morbidity for clipping and coiling-treatment of symptomatic aneurysms elevates the procedural risk. IAR was less frequent during coiling, but was associated with relevant mortality. IAR and periprocedural ischemia represent significant treatment-associated risks, which should be taken into account in interdisciplinary treatment planning and patient counseling.