Both the population of siblings of youth with developmental disabilities (DDs) and the popularity of clinical services designed for these youth are on the rise. However, the research base for such services has yet to be evaluated. A systematic review of studies on intervention and support for siblings of youth with DDs was conducted in order to evaluate the current state of the literature and provide recommendations for research and practice. Sixteen articles were selected and reviewed in terms of their experimental design, participant characteristics, measurement, intervention or support group protocol, outcomes, and dissemination of findings. Results indicate substantial variability in both methodology and outcomes across sibling-focused intervention and support group studies, which put the overall effects and utility of these services into question. Recommendations for future research are outlined, with a focus on advancing a more systematic and careful approach to asking and effectively answering questions about siblings, their families, and meaningful services for both.