Neurodevelopment in children with congenital hypothyroidism who receive early treatment is generally good. However, subtle neurological deficits still exist in some patients. The aim of this investigation was to evaluate factors that may influence neurodevelopmental outcome in congenital hypothyroidism patients. The developmental quotient (DQ) of 155 children with congenital hypothyroidism was evaluated at 24 months of age, using Gesell Developmental Schedules (GDS), and compared with that of 310 healthy controls. Mean DQ scores in congenital hypothyroidism patients were 7.5 points lower for adaptive behavior than in control patients (p < 0.01). Patients with severe congenital hypothyroidism had the lowest DQ scores compared with two other congenital hypothyroidism subgroups and controls (p < 0.01). Children with congenital hypothyroidism who also had a low level of serum T(4) at diagnosis or exhibited a longer thyroid stimulating hormone (TSH) normalization time had lower adaptive behavior scores (p < 0.0003). Bivariate correlation and multiple regression analyses found that the severity of congenital hypothyroidism and parental socioeconomic status correlated with DQ scores. TSH normalization time was negatively related to adaptive behavior scores (p < 0.01). Neurodevelopmental deficits in children with congenital hypothyroidism correlate with the severity of congenital hypothyroidism, TSH normalization time, and parental socioeconomic status.