Parents of 30 school-age children with Down syndrome participated in a small-scale randomized clinical trial of a behavioral sleep treatment designed specifically for children with Down syndrome. The aim was to improve child sleep, child daytime behavior problems, caregiver sleep, and caregiver stress. The intervention spanned 5-8 weeks, and assessments occurred pre-treatment, immediately post-treatment, and three months post-treatment using a double-blinded design. Both the active treatment and a treatment-as-usual attention-controlled comparison group showed improvements in actigraphy and parent-report measures of child sleep, parent-reported child internalizing behaviors, and actigraphy measures of parent-sleep. The behavioral sleep treatment did not yield significantly different outcomes than a treatment-as-usual approach supplemented with non-sleep-specific behavioral or education sessions. Possible interpretations of study findings are discussed.