Self-advocacy is a critical predictor of actual physical activity participation for children and adolescents with disabilities. Despite its reference within national standards for health and physical education, few practitioners are purported to promote self-advocacy among their students warranting the need for evaluation. However, no self-advocacy inventory exists for children and adolescents with robust psychometrics properties. The purpose of this study was to investigate the content and face validity for the Physical Activity Self-Advocacy Inventory (PASAI) within children and adolescents with and without disabilities. Experts in the fields of health and physical education (N = 12) participated in this Delphi study. Once experts established the content/face validity for the PASAI, children and adolescents (N = 18) provided feedback on the PASAI to further refine the questions and support comprehension/relevance for the target population. After the first round of questions, experts' average feedback was a 3.99 out of 5.00 across all items. Due to low scores and based upon experts' suggestions, four questions were deleted, and one question was added. After round two, experts' average ratings increased to 4.8 out of 5.00. The PASAI appears to have reasonable content/face validity properties per expert- and population-based feedback. Future research should vet additional psychometric properties of PASAI scores.