Background: Previous research has highlighted the importance of the transition to school for young children and their families. A child's successful adaptation to school is likely influenced by a number of factors, including academic, social, emotional, behavioural and cognitive competencies. Children with intellectual disability (ID) may be at heightened risk for early school difficulties, in part due to their deficits in cognitive and adaptive behaviours. Methods: Factors associated with the adaptive transition to school in young children with (n=24) and without (n=43) ID were examined. Adaptive transitions were defined as having few teacher-reported problem behaviours and positive student-teacher relationships. Child self-regulatory skills and both parent- and teacher-reported social skills were evaluated to determine if they predicted positive adaptation in school for 5- to 6-year-old children. Data were gathered from child assessments, parent reports on standardized measures, direct observations of delay of gratification tasks and teacher reports on standardized measures. Results: Children with ID had significantly more teacher-reported problem behaviour, poorer overall student-teacher relationships, fewer parent- and teacher-reported social skills and fewer self-regulation skills than typically developing children. Self-regulation at child age 36months (latency to touch a desired toy) was significantly related to adaptation to school, as were parent and teacher reports of social skills. Social skills significantly predicted adaptation to school, even after accounting for the effects of child IQ and adaptive behaviour. Conclusions: Children with ID had less positive early school experiences, as indicated by multiple indices of adaptation to school. Fostering early social skills may be an important target for increasing the positive adaptation to school for young children, especially those with ID.