Background: Effective management of key physiological parameters, such as blood pressure, temperature, blood glucose, and gas exchange, is central to neurocritical care. However, the clinical impact of variability within guideline target ranges after an acute ischemic stroke, intracerebral hemorrhage, or subarachnoid hemorrhage remains unclear. Methods: In this multicenter observational study of nine German neurocritical care units, we analyzed in-range measurements over 96 h. Of 524 screened patients, 281 met the predefined criteria for sufficient in-range data. Variability in systolic blood pressure, mean arterial pressure, body temperature, blood glucose, partial arterial pressure of oxygen and carbon dioxide was quantified using the coefficient of variation. Associations between in-range variability of each physiological parameter and clinical outcomes including duration of mechanical ventilation, NIHSS score at discharge, and in-hospital mortality were evaluated using multivariable regression models. Results: Variability for all parameters peaked in the first 24 h and then remained largely stable; blood glucose showed a secondary rise after ~60 h. Greater in-range blood glucose variability was associated with in-hospital mortality in hemorrhagic stroke (adjusted OR 1.08; 95% CI 1.00-1.17; p = 0.04), while no other parameter's variability was associated with the evaluated outcomes. Conclusions: Overall, in-range variability had limited short-term prognostic value, supporting current guideline-based management.