The prevalence of autism spectrum disorder (ASD) in boys is nearly four times higher than in girls, and the causes of this sex difference are not fully known. Difficulties in executive function may be involved in development of autistic symptomatology. Here we investigated sex differences in the relationship between executive function in everyday life and social dysfunction symptoms in a sample of 116 children (25 girls) aged 5-19 years with IQ above 70 and with a diagnosis of ASD. They were assessed with the Behavior Rating Inventory of Executive Function (BRIEF) and the Autism Diagnostic Interview Revised (ADI-R). We found no significant differences in BRIEF or ADI-R scores between girls and boys after correcting for multiple testing. Nested linear regression models revealed significant sex differences in the relationship between executive function and both reciprocal social interaction and communication over and above the main effects of age, sex, IQ and comorbid attention deficit/hyperactivity disorder diagnosis. We did not find sex differences in the relationship between executive dysfunction and restricted and repetitive behaviors. Altogether, our results provide a greater understanding of the sex-specific characteristics of ASD and may suggest that boys and girls can benefit from different intervention strategies.