Objective: To define the incidence of ventriculostomy-associated infections and their impact on the mortality and functional outcomes of patients with aneurysmal subarachnoid hemorrhage. Methods: We prospectively included all consecutive adult aneurysmal subarachnoid hemorrhage patients admitted to the neurological intensive care units of the Instituto Estadual do Cérebro Paulo Niemeyer (Rio de Janeiro, Brazil) and Hospital Cristo Redentor (Rio Grande do Sul, Brazil) who required external ventricular drains from July 2015 to December 2020. Daily clinical and laboratory variables were collected at admission and during the hospital stay. The presence of ventriculostomy-associated infections was evaluated daily, according to the Centers for Disease Control and Prevention and Infectious Diseases Society of America criteria. Hospital and 12-month outcomes were compared between patients with and without ventriculostomy-associated infections via both univariate and multivariate analyses. Results: Out of the 676 patients screened, 271 received external ventricular drains (40%) and were included in the study. The mean age was 54 years (IQR 46-63), 198 were female (72%), 47% had poor grade status (World Federation of Neurological Surgeons scale 4 and 5), and 75% had modified Fisher 3 or 4. The mean time from admission to external ventricular drain placement was 8.8 days. Ventriculostomy-associated infections developed in 127 patients (47%), and the mean time from external ventricular drain to ventriculostomy-associated infection diagnosis was 4.4 days. Hospital and 12-month mortality rates did not differ between the ventriculostomy-associated infection group and the nonventriculostomy-associated infection group (36% versus 40% and 43% versus 49%, respectively). Poor functional outcomes, defined as modified Rankin scores of 4 to 6, showed no difference between groups at hospital discharge (ventriculostomy-associated infections 75% versus nonventriculostomy-associated infections 73%; p = NS) or at 12 months (ventriculostomy-associated infections 49% versus nonventriculostomy-associated infections 53%; p = NS). Conclusion: Ventriculostomy-associated infections are common complications after aneurysmal subarachnoid hemorrhage. Although it was not associated with hospital mortality or functional outcomes in our cohort, improving diagnostic accuracy and preventive measures is essential for better understanding the long-term impact of one of the most severe infectious complications after aneurysmal subarachnoid hemorrhage.