This paper reports a case-control study of a horse riding intervention for children with autism spectrum disorder (ASD). A sample of 26 children, aged 6 to 9 years, were assigned to either the intervention (n = 12) or control group conditions (n = 14). Pre- and post-tests were carried out using the Childhood Autism Rating Scale, Second Edition (CARS2) and the Aberrant Behaviour Checklist-Community Edition (ABC-C). An observational measure of compliance and behaviour during the horse riding sessions was completed for the intervention group. There was a significant reduction in the severity of ASD symptoms and hyperactivity from pre- to post-test for the intervention group only. These results indicate that the intervention improves some aspects of social functioning for children with ASD.