Although the conception of autism as a disorder of abnormal resting-state physiology has a long history, the evidence remains mixed. Using state-of-the-art eye-tracking pupillometry, resting-state (tonic) pupil size was measured in children with and without autism. No group differences in tonic pupil size were found, and tonic pupil size was not related to age or cognitive ability in either group, and nor was it related to autistic symptoms. We suggest that previous findings of hyper-arousal in autism at baseline may be a product of different recording methods, in particular different movement-artifact removal techniques. These results question the notion that autism is associated with a fundamental dysregulation in resting-state physiology. Further research, employing such techniques is needed to confirm these findings.