Research findings describing the emotional and behavioral functioning of typically developing (TD) siblings of children with autism spectrum disorders (ASD) are contradictory. Methodological issues, such as small study sample sizes and reliance on parent report, may contribute to inconsistent findings. The purpose of this study was to use parent and teacher report to describe presence of internalizing and externalizing behaviors among a large sample (n = 486) of TD siblings of children with ASD. Results indicated that siblings did not exhibit a disproportionate prevalence of internalizing or externalizing symptoms in comparison to the standardization sample of the rating scale. The presence of a sibling with an ASD may not be considered a risk-factor for adjustment problems among TD siblings.