This paper describes the outcomes of a 6-week family-based psycho-educational intervention for siblings of children with a disability or chronic illness. A randomised controlled trial method was used with 21 siblings (aged 8-16 years) and their parents. Results revealed a decrease in siblings’ emotional symptoms, perceived intensity of daily stress, and use of avoidant coping; a strengthening of family time and routines; and high parental satisfaction with the program. Given the limited number of well-controlled sibling intervention studies, this research is an important step towards developing empirically supported sibling interventions, and is of significance to professionals working with families of children with a disability or chronic illness.