Cognitive and behavioral flexibility are important predictors of adaptive behavior in school-age autistic youth. While prior research has utilized broad measures of flexibility, the current study uses the multi-dimensional Flexibility Scale-Revised to examine which specific flexibility skills relate to adaptive functioning. Through parent-report measures on 216 autistic youth, flexibility explained 22.2% of variance in adaptive socialization skills (p < 0.001). Specifically, Social Flexibility accounted for significant variance in adaptive socialization skills, while Transitions/Change approached significance. In exploratory analyses, flexibility explained 11.5% of variance in Communication skills (p < 0.001). This pattern remained after controlling for co-occurring ADHD symptoms. The current study helps to refine the relationship between flexibility and adaptive behavior, which may ultimately help to inform more targeted interventions.