© 2020 Elsevier Inc. Objective: To assess outcomes following post-hemorrhagic ventricular dilatation (PHVD) among infants born at ≤26 weeks of gestation. Study design: Observational study of infants born April 1, 2011, to December 31, 2015, in the Eunice Kennedy Shriver National Institute of Child Health and Human Development Neonatal Research Network and categorized into 3 groups: PHVD, intracranial hemorrhage without ventricular dilatation, or normal head ultrasound. PHVD was treated per center practice. Neurodevelopmental impairment at 18-26 months was defined by cerebral palsy, Bayley Scales of Infant and Toddler Development, 3rd edition, cognitive or motor score <70, blindness, or deafness. Multivariable logistic regression examined the association of death or impairment, adjusting for neonatal course, center, maternal education, and parenchymal hemorrhage. Results: Of 4216 infants, 815 had PHVD, 769 had hemorrhage without ventricular dilatation, and 2632 had normal head ultrasounds. Progressive dilatation occurred among 119 of 815 infants; the initial intervention in 66 infants was reservoir placement and 53 had ventriculoperitoneal shunt placement. Death or impairment occurred among 68%, 39%, and 28% of infants with PHVD, hemorrhage without dilatation, and normal head ultrasound, respectively; aOR (95% CI) were 4.6 (3.8-5.7) PHVD vs normal head ultrasound scan and 2.98 (2.3-3.8) for PHVD vs hemorrhage without dilatation. Death or impairment was more frequent with intervention for progressive dilatation vs no intervention (80% vs 65%; aOR 2.2 [1.38-3.8]). Death or impairment increased with parenchymal hemorrhage, intervention for PHVD, male sex, and surgery for retinopathy; odds decreased with each additional gestational week. Conclusions: PHVD was associated with high rates of death or impairment among infants with gestational ages ≤26 weeks; risk was further increased among those with progressive ventricular dilation requiring intervention.