Research in autism spectrum disorders (ASD) described individual differences in response to intervention. This study explored child and parental characteristics at baseline that predict outcomes in adaptive skills and acquisition of cognitive gains. Seventy-eight children aged 15-35 months diagnosed with ASD by standardized diagnostic tools were included. Evaluations of verbal and non-verbal abilities, adaptive skills and autism severity were obtained at pre-intervention (T1) and after one year of intervention (T2). At T2, children improved significantly in their verbal ability and the severity of autism symptoms was reduced. Outcome in adaptive skills was best predicted by baseline verbal ability and maternal age. Better verbal ability especially in those with severe autism symptoms, and older maternal age predicted better adaptive skills outcome. T1 autism severity, child's age and maternal age and educational attainment best predicted cognitive gains. Less severe autism symptoms, younger child's age at start of intervention, older maternal age and higher maternal education predicted greater cognitive gains with intervention. The study suggests biological factors including age, language abilities and autism severity and environmental factors including maternal age and education, impact the ability to benefit from early intervention in ASD. (Contains 3 tables.)