This study examined risk factors for behavioral and emotional problems in 1973 siblings of children with autism spectrum disorders (ASD). Results revealed six correlates of sibling internalizing and externalizing problems: male gender, smaller family size, older age of the child with ASD, lower family income, child with ASD behavior problems, and sibling Broader Autism Phenotype. Siblings with few risk factors were at low risk for behavioral and emotional problems. However, siblings with many risk factors were at increased risk for both internalizing and externalizing problems. These results highlight the need to assess risk for individual siblings to best identify a sub-population of siblings who may be in need of additional support.