Pivotal Response Treatment (PRT) is an empirically based behavioral treatment for children with autism spectrum disorders (ASD). Using parent-child dyads as the mode of intervention, parents are taught specific motivational treatment skills to use with their children with ASD. When conducting PRT in the home, there exist the additional complexities of everyday living such as the presence of siblings. A sibling who exhibits disruptive behavior in an effort to gain the parent's attention can result in the treatment session being interrupted. There is little research to date on how to mitigate the difficulties of implementing PRT when there is a disruptive sibling present. The current study employed a multiple baseline design to compare the traditional parent-child dyad model to an intervention tailored to the needs of the sibling in addition to the conventional dyad. Three triads participated in this study: a 3-year-old child with ASD and her typically-developing 5-year-old brother and their mother, a 10-year-old child with ASD and his typically-developing 7-year-old brother and their mother, and a 9-year-old with ASD and his typically-developing 4-year-old brother and their mother. The results showed that with an intervention that addressed the siblings' needs, the frequency of sibling disruptive behavior decreased. The intervention also resulted in an increase of positive affect for the mother, child with ASD, and the sibling, and did not detract from the presentation of treatment opportunities for the children with ASD to work towards their respective treatment goals. Furthermore, the children with ASD made progress towards their respective treatment goals. These results generalized and maintained. The findings are discussed with regard to theoretical and clinical significance.