Joint attention is pivotal to the development of complex social skills and language, and many individuals with Autism Spectrum Disorders display deficits in this domain. Behavioral interventions targeting joint attention are evidenced to be effective in teaching these skills to young children with autism, but these treatments have traditionally been implemented by adults in structured settings. Concerns regarding the generalizability of skills acquired under such conditions have been raised. Four typically developing children were trained to implement a joint attention intervention to their siblings with autism in the home. Joint attention was measured pre-treatment and post-treatment during play sessions and during a structured, adult-mediated assessment to evaluate maintenance and generalization. Gains in responding to joint attention were observed for all four participants; gains in initiations were observed in three participants. Rates of imitation and behavioral requests also increased in structured and naturalistic settings. This study supports the efficacy of siblings as interventionists to target complex social skills in the natural environment. The implications of these findings for treatments targeting joint attention and for siblings as interventionists are discussed. Copyright © 2011 John Wiley & Sons, Ltd.