"Joint action"-the ability to coordinate actions with others-is critical for achieving individual and interpersonal goals and for our collective success as a species. Joint actions require accurate and rapid inferences about others' goals, intentions, and focus of attention, skills that are thought to be impaired in individuals with autism spectrum disorder (ASD). Research to date has not investigated joint action abilities in individuals with ASD during real-world social interactions. We conducted an experimental study that required children with ASD and typically developing children to move tables by themselves or collaboratively through a maze. This involved developing innovative methodologies for measuring action coordination-a critical component of the joint action process. We found that children with ASD are less likely to benefit from the collaboration of a peer than are typically developing children, and they are less likely to synchronize their steps when moving the table. However, these differences were masked when scaffolded by an adult. There was no evidence that ASD differences were due to gross motor delays in the participants with ASD. We argue that action coordination is a highly adaptive social process that is intrinsic to successful human functioning that manifests as atypical synchronization of mind and body in children with ASD.