Background: Congenital hyperinsulinism (CHI) is hallmarked by persistent hypoketotic hypoglycemia in infancy. In the majority of all patients, CHI is caused by mutations in the KATP channel genes ABCC8 and KCNJ11, but other genes in the insulin-regulatory pathway have also been described. Repeated episodes of hypoglycemia include an increased risk of seizures and intellectual disability. So far, controlled psychometric studies on cognitive, motor, speech, and social-emotional outcome of CHI patients are missing. Until now, neurodevelopmental long-term outcome in CHI patients has only been measured by questionnaires, self-, parental-, or caregiver-administered instruments. Methods: This is a prospective study of 60 patients (median age 3.3 years, range 3 months to 57 years): 48 with a diffuse, 9 with a focal, and 3 with an atypical histology. Neurodevelopmental outcome was assessed using standardized psychological tests and questionnaires. Results: 28 of 60 patients showed developmental delay (46.7%). 9 of 57 patients had cognitive deficits (15.8%), 7 of 26 patients had speech problems (26.9%), and 17 of 44 patients had motor problems (38.6%). In 5 of 53 patients, social-emotional problems were reported. Outcome and the underlying genetic defect were not correlated. Conclusions: Motor problems seem to be prominent in CHI patients. Despite a high incidence of developmental delay, a permanent cognitive defect was only detectable in 9 of 58 patients.