Background: Early permanent cerebrospinal fluid (CSF) diversion for hydrocephalus after aneurysmal subarachnoid hemorrhage (aSAH) might shorten the duration of external ventricular drainage (EVD) and thereby reduce infectious complications. The potential effect on the rate of delayed cerebral vasospasm (DCVS) and associated morbidity has not been studied to date. The objective of this study was to detect any association with EVD-associated infections (EVDAI), symptomatic DCVS, or delayed cerebral ischemia (DCI) by the time of hospital discharge. Methods: A single-center dataset of aSAH patients who received a permanent CSF diversion procedure between 2009 and 2018 was used for the evaluation. The subjects were divided into an “early group” if such a procedure was performed up to 14 days after the ictus, and a “late group” if it was performed from the 15 th day onward. The statistical analysis employed univariable and multivariable logistic regression models. Results: Among 274 consecutive aSAH patients, 39 (14.2 %) had a permanent CSF diversion procedure. While the blood clot burden was similarly distributed, patients with early permanent CSF diversion (20 out of 39, 51.2%) had higher levels of consciousness on admission. Early permanent CSF diversion was associated with a shorter duration of EVD (OR 0.73, 95%CI 0.58-0.92 per day). Higher catheter colonization to EVDAI ratio (1/7 out of 20 vs. 7/7 out of 19) and a markedly lower frequency of EVDAI (OR 0.08, 95 %CI 0.01-0.80) were detected. The prevalence (5 vs. 37) and the cumulative incidence (3 vs. 18) of EVDAI were remarkably lower in patients receiving early permanent CSF diversion. The occurrence of CSF-diversion device obstruction, the rate of symptomatic DCVS (OR 0.61, 95 %CI 0.16-2.27) or detected DCI on computed tomography (OR 0.35, 95 %CI 0.08-1.47), and the likelihood of a poor outcome at discharge did not differ between the two groups (OR 0.88, 95%CI 0.24-3.22). Conclusions: Early permanent CSF diversion in good grade aSAH patients is associated with a shorter duration of EVD, lower catheter colonization rates, and fewer infectious complications. The timing of permanent CSF diversion had no detectable effect on DCVS-related morbidity. These findings need to be confirmed in larger cohorts.