Debate is ongoing about whether typically developing siblings of children with autism spectrum disorder (ASD) are at greater risk of behavioral or emotional problems than siblings of children without ASD. Most data on behavior is provided by mothers, and we do not know whether fathers’ reports differ. The strengths and difficulties questionnaire (Goodman in J Child Psychol Psychiatry 38(5):581-586, 1997) was completed by 168 mothers and 130 fathers. Parents were more likely to rate siblings as having ‘abnormal’ behavior when compared to a normative population. We found moderate correlations between mother-father ratings. More research may be needed to understand any clinical benefits of gathering data about sibling adjustment from more than one parent in the family. Implications for clinical practice and future research are discussed.