Background/Objectives: To propose a novel definition for hydrocephalus growth and to further describe the association between hydrocephalus growth and poor outcome among patients with intracerebral hemorrhage (ICH). Methods: We analyzed consecutive patients who presented within 6 h after ICH ictus between July 2011 and June 2017. Follow-up CT scans were performed within 36 h after initial CT scans. The degree of hydrocephalus were evaluated by the hydrocephalus score of Diringer et al. The optimal increase of the hydrocephalus scores between initial and follow-up CT scan was estimated to define hydrocephalus growth. Poor long-term outcome was defined as a modified Rankin Scale of 4–6 at 3 months. Multivariate logistic regression analysis was performed to investigate the hydrocephalus growth for predicting 30-day mortality, 90-day mortality, and poor long-term outcome. Results: A total of 321 patients with ICH were included in the study. Of 64 patients with hydrocephalus growth, 34 (53.1%) patients presented with both concurrent hematoma expansion and intraventricular hemorrhage (IVH) growth. After adjusting for potential confounding factors, hydrocephalus growth independently predicted 30-day mortality, 90-day mortality, and 90-day poor long-term outcome in multivariate logistic regression analysis. Hydrocephalus growth showed higher accuracy for predicting 30-day mortality, 90-day mortality, and poor long-term outcome than IVH growth or hematoma expansion, respectively. Conclusions: Hydrocephalus growth is defined by strongly predictive of short- or long-term mortality and poor outcome at 90 days, and might be a potential indicator for assisting clinicians for clinical decision-making. [ABSTRACT FROM AUTHOR]