Later-born siblings of children with Autism Spectrum Disorders (ASD) are at increased risk for ASD as well as qualitatively similar traits not meeting clinical cutoffs for the disorder. This study examined age five neurocognitive and behavioral outcomes of 39 younger siblings of children with ASD (Sibs-ASD) and 22 younger siblings of typically developing children (Sibs-TD) previously assessed in a longitudinal investigation starting in the second year of life. There were few group differences between Sibs-TD and Sibs-ASD on global measures of IQ, language, or behavior problems. Sibs-ASD did show vulnerabilities on measures of executive functioning, social cognition, and repetitive behaviors. These results highlight the importance of following sibling risk groups over an extended time period and employing measures targeting broader aspects of development. © 2011 Springer Science+Business Media, LLC.