This study examined associations between sibling temperaments, differential parenting, and the quality of the relationships between 50 children with autism spectrum disorder (ASD) and their typically developing siblings. The temperament dimension of persistence, but not activity level or emotional intensity, was found to relate to the quality of the sibling relationship. Effects were stronger for temperaments of the typically developing siblings, but persistence levels of both groups of children interacted to predict sibling relationship quality. Persistence also was the temperament dimension associated with differential parenting, with increased levels of differential parenting occurring when siblings, and to some degree the children with ASD, were low in persistence. When siblings were dissatisfied with differential parenting, quality of the sibling relationship was compromised.