The expectations and role of families in the care of children with autism spectrum disorder are increasingly important. Nonetheless, no study has thus far explored the perspectives of siblings about the care received by a brother or sister with this disorder. The objective of this study was to fill this gap in the literature. This multicentre qualitative study took place in France, where we conducted semi-structured interviews with adolescents who were older siblings of children receiving care in a day hospital for an autism spectrum disorder. Data collection by "purposive sampling" continued until we reached 'theoretical sufficiency', and data analysis was thematic. The study included 20 participants: 13 sisters and 7 brothers. Four themes emerged in the data analysis: (1) the treatment targets, (2) the treatment's perceived effectiveness, (3) the complex questions it raises and (4) the role of intrafamily relationships. Our results allowed us to report original aspects of the experience of siblings, in particular, their confusion with regard to the treatment, their difficulty in separating themselves from their parents' discourse and their assertion of their role as caregivers for their younger brothers and sisters.