Objectives Despite recent advances in the treatment of children with univentricular heart, their neurodevelopmental outcome remains a major concern. Methods This prospective follow-up study evaluated the neurodevelopmental outcome of 23 patients with hypoplastic left heart syndrome, 14 with other forms of univentricular heart, and 46 healthy control subjects at a median age of 12.2 months. The Griffiths Developmental Scale and Alberta Infant Motor Scale served for developmental evaluation. Results The mean Griffiths developmental quotient of children with hypoplastic left heart syndrome was significantly less (91.6) than that of control children (106.8, P < .001). Patients with univentricular heart scored significantly lower than control subjects only in the gross motor domain ( P = .001) but not in overall development (100.6). Alberta Infant Motor Scale scores were significantly lower in children with hypoplastic left heart syndrome (37.5, P < .001) and univentricular heart (43.5, P = .011) than in control subjects (53.3). In linear regression a diagnosis of hypoplastic left heart syndrome ( P = .016), a clinical history of seizure ( P = .002), and the highest plasma lactate level after the bidirectional Glenn operation ( P = .045) were significantly associated with the developmental quotient. Conclusions At age 1 year, the level of development of children with univentricular heart was significantly lower than for control subjects only in motor skills, whereas children with hypoplastic left heart syndrome had a more widespread developmental delay. The diagnosis, a clinical seizure history, and increased plasma lactate levels after the bidirectional Glenn operation emerged as risk factors.