Autistic social challenges have long been assumed to arise from a lack of social knowledge (“not knowing what to do”), which has undergirded theory and practice in assessment, treatment, and education. However, emerging evidence suggests these differences may be better accounted for by difficulties with social performance (“doing what they may know”). This distinction has important implications for research, practice, policy, and community support of autistic people. This review examines the theoretical and clinical implications and empirical status of the knowledge-performance distinction in autism. Current evidence suggests that social knowledge deficits are neither definitional nor reliably related to outcomes in autism. Prioritizing social knowledge, then, may produce unanticipated, problematic consequences in terms of accuracy of assessment, intervention effectiveness, and promotion of stigma. It may also yield unrealistic expectations around the value of knowledge for autistic people and their families, yielding important ethical considerations. Conversely, recent evidence highlights performance-related factors as being especially promising for better modeling and addressing social challenges in autism. Prioritizing performance, then, may offer new directions for assessment, substantially different intervention opportunities, and novel methods of inclusion and affirmation. This review touches upon each of these domains and implications, integrates these developments with broader models of social competence in youth, and provides direction for future research and practice regarding social competence in autism.