BACKGROUND: Studies of early childhood outcomes of mild hypoxic-ischemic encephalopathy (HIE) identified in the first 6 h of life are lacking. OBJECTIVE: To evaluate neurodevelopmental outcomes at 18-22 months of PRIME study. STUDY DESIGN: Multicenter, prospective study of mild HIE defined as ≥1 abnormality using the modified Sarnat within 6 h of birth and not meeting cooling criteria. Primary outcome was disability with mild: Bayley III cognitive 70-84 or ≥85 and either Gross Motor Function Classification System (GMFCS) 1 or 2, seizures, or hearing deficit; moderate: cognitive 70-84 and either GMFCS 2, seizures, or hearing deficit; severe: cognitive <70, GMFCS 3-5. RESULTS: Of the 63 infants enrolled, 51 (81%) were evaluated at 19 ± 2 months and 43 (68%) completed Bayley III. Of the 43 infants, 7 (16%) were diagnosed with disability, including 1 cerebral palsy and 2 autism. Bayley scores < 85 in either cognition, motor, or language were detected in 17 (40%): 14 (32%) language, 7 (16%) cognitive, and 6 (14%) motor domain. Infants with disability had more abnormalities on discharge examination and brain MRI, with longer hospital stay (p < 0.001). CONCLUSIONS: In this contemporary untreated cohort of mild HIE, disability occurred in 16% of infants at 18-22 months.