This RCT investigated whether the effect of a Theory of Mind (ToM) intervention for children with ASD was moderated by parental education level and employment, family structure, and parental ASD. Children with autism aged 8-13 years (n = 136) were randomized over a waitlist control or treatment condition. At posttest, children in the treatment condition had more ToM knowledge, showed fewer autistic features, and more ToM-related behavior than children in the control condition. Children who had one or two parents with at least a college degree, and children with parents not diagnosed with/suspected of having ASD themselves benefitted from the training. These findings provide valuable information about family variables that need to be taken into account in treatment design and implementation.