The study aimed to develop and validate a nomogram to identify suspected post-neurosurgical bacterial ventriculitis/meningitis (BV/M) in patients with cerebrospinal fluid (CSF) leukocytes ≥ 100/mm³ and glucose ≤ 2.2 mmol/L. Out of 711 suspected patients, 271 adults (150 with confirmed BV/M and 121 without BV/M) from three hospitals were selected for the training cohort. Using multivariate logistic regression, six independent predictors were identified: CSF glucose, CSF leukocytes, CSF erythrocytes, CSF neutrophil ratio, blood lymphocyte ratio, and external ventricular drainage. The nomogram was validated in two independent cohorts (84 and 58 patients) including the MIMIC-III and MIMIC-IV databases, where it demonstrated high discriminative power. In high-risk patients, immediate administration of antibiotics is recommended, while in low-risk patients, more frequent CSF testing is suggested before treatment.