Background: Responses to digital cognitive training interventions vary greatly among children with intellectual and developmental disorders (IDD). Investigating possible predictors of improvements following training is vital in ascertaining which individuals benefit from these interventions. Methods: Seventy-three children (4-11 years) with IDD completed attention training or a placebo program for 5 weeks. The effects of autistic symptomatology, adaptive functioning and pre-intervention attention abilities on improvements in attention (selective and sustained) post-intervention were examined. Results: Autistic symptomatology did not predict any training improvement. However, lower adaptive functioning predicted greater gains in selective attention post-intervention in children who received training compared to placebo. Further, better pre-intervention selective attention performance was associated with greater improvements in selective attention post-intervention. Conclusions: Although these findings are exploratory, attention training may be beneficial for children with IDD with lower adaptive functioning and higher pre-intervention attention abilities.