Objective: To investigate the role of cerebrospinal fluid (CSF) and serum procalcitonin (PCT) in diagnosis of post-neurosurgical bacterial meningitis/ventriculitis (PNBM/BV) in patients with aneurysmal subarachnoid hemorrhage (aSAH). Methods: A prospective observational study was conducted, and 53 patients with suspected bacterial meningitis after craniotomy were selected from June 2018 to June 2019 in Department of Neurosurgical Intensive Care Unit in Xuanwu Hospital of Capital Medical University. The patients were divided into PNBM/BM group (25 cases) and non-PNBM/BV group (NPNBM/BV, 28 cases). CSF cells count, white blood cell count (WBC), protein quantity and glucose, blood glucose and CSF/blood glucose ratio, and CSF and serum PCT were measured. Pearson correlation analysis and partial correlation analysis were used to explore the correlation between CSF PCT and CSF and serum indicators. The receiver operating characteristic curve (ROC curve) and calculate the area under the curve (AUC) were drawn, and the sensitivity and specificity of CSF and serum PCT in the diagnosis of PNBM/BV were calculated. Results: CSF WBC (P=0.011), protein quantity (P=0.030), PCT (P=0.000) and serum PCT (P=0.010) in PNBM/BV group were higher than those in non-PNBM/BV group, while CSF glucose (P=0.000) and CSF/serum glucose ratio (P=0.000) in PNBM/BV group were lower than those in non-PNBM/BV group. Correlation analysis showed that PCT in CSF was positively correlated with serum PCT (r=0.421, P=0.002) and CSF WBC (r=0.394, P=0.004), but negatively correlated with CSF glucose (r=-0.327, P=0.018). The ROC curve showed the AUC of CSF PCT in the diagnosis of PNBM/BV was 0.835 (95% CI:0.710-0.960, P=0.000), the sensitivity was 88%, the specificity was 82.10%, the positive predictive value was 81.48% (22/27), the negative predictive value was 88.46% (23/26), and the diagnostic cutoff value was 0.331 ng/ml. The ROC curve showed the AUC of serum PCT for the diagnosis of PNBM/BV was 0.720 (95% CI:0.580-0.860, P=0.000), the sensitivity was 64%, the specificity was 75%, the positive predictive value was 69.57% (16/23), the negative predictive value was 70% (21/30), and the diagnostic cutoff value was 0.501 ng/ml. Conclusions: Detection of CSF and serum PCT has important clinical application value in the diagnosis of PNBM/BV after aSAH. Copyright © 2020 by the Editorial Board of Chinese Journal of Contemporary Neurology and Neurosurgery.