Objective: Theory suggests that impaired executive functioning (EF) might explain several symptoms of autism spectrum disorder (ASD) in children. However, only a few studies have examined the efficacy of EF training for the children using randomized control trial designs, and only two of them found significant benefits of the training. Method: We designed Comprehensive Attention Training System (CATS), and tested this new EF intervention for children with ASD in a small-sampled randomized controlled trial. Twenty-five children with ASD aged six to twelve were randomly assigned to either the CATS or the control training and were assessed pre- and post-training. Results: Relative to the control group, the CATS group improved on EF as measured by the trail-making test, avoiding perseverative errors, and forming conceptual responses in the Wisconsin Card Sorting Task. There were also indications that CATS contributed to long-term communication skills as measured by the Vineland adaptive behavior scales. Conclusions: We report preliminary evidence that the CATS intervention may improve the EF of school-aged children with ASD compared to a control intervention. We discuss the results in terms of their generalizability to other developmental disorders.