To effectively combat high levels of inactivity among children with autism spectrum disorder (ASD), scalable and sustainable methods of intervention are required. The purpose of this study was to examine the feasibility of a web-based, parent-mediated physical activity intervention for thirteen children with ASD. The intervention, Project CHASE, involved parents joining a private Facebook group where they were exposed to five intervention components, based on the social cognitive theory. The primary outcome of interest was the feasibility and perceived effectiveness of, and engagement with, the intervention, as measured by a parent-completed questionnaire and activity within the Facebook group. The analysis focused on descriptive statistics, rather than inferential statistics. Participants reported Project CHASE to be a feasible means of supporting their child's physical activity, with all participants reporting being satisfied or very satisfied with their 'overall experience', and finding the content interesting and useful. Over 75% of the sample reported the weekly goals, physical activity reporting, information on physical activity opportunities and ideas, and posting/viewing pictures of children being active to be effective or very effective components. Suggestions are provided for the refinement of Project CHASE, and how the results can inform future web-based physical activity interventions for youth with ASD.