Executive functioning is thought to contribute to adaptive behavior skills development in individuals with autism spectrum disorder (ASD). However, supporting data are largely based on caregiver reports of executive functioning. The current study evaluated whether performance-based measures of executive functioning (working memory and inhibition) explained unique variance in parent-reported adaptive functioning among youth with ASD without an intellectual disability. Both spatial and verbal working memory were associated with adaptive functioning, particularly communication and daily living skills. Our findings demonstrate a robust relationship between working memory and adaptive functioning that translates across different measurement modalities. This preliminary study highlights that targeting executive functioning may be a critical component of an adaptive function training program. [Additional funding for this research was provided by the Intellectual and Developmental Disabilities Research Center at Children's National Medical Center and the National Institutes of Health General Clinical Research Center.]