Younger siblings of children with autism spectrum disorder (ASD; high-risk siblings) are at elevated risk for developing the broader autism phenotype (BAP), which consists of subclinical features of ASD. We examined conversational skills in a naturalistic context and standardized assessments of pragmatic language and communication skills in high-risk and low-risk school-age children with BAP (n = 22) and ASD (n = 18) outcomes, as well as comparison children without ASD or BAP (n = 135). Children with BAP characteristics exhibited lower conversational skills than comparison children, but did not differ on any of three standardized measures. Only the conversational ratings significantly predicted membership in the BAP versus Comparison group. This suggests that naturalistic tasks are crucial when assessing social-communication difficulties in children with a family history of ASD. LAY SUMMARY: The broader autism phenotype (BAP) consists of subclinical features of autism spectrum disorder (ASD) and is more common among family members of those with ASD. School-age children with BAP characteristics exhibited lower conversational skills than comparison children, but did not differ on standardized language measures tapping similar abilities. This suggests that naturalistic tasks may be more sensitive to the social-communication difficulties seen in some children with a family history of ASD than the standardized language tests used in most evaluations. © 2021 International Society for Autism Research and Wiley Periodicals LLC.