Pediatric anxiety disorders (AD) are prevalent disorders with an impact on all aspects of a child’s life and functioning.1 Although evidence supports commonly used treatments, there are notable concerns with the research to date.2 Heterogeneity in outcome selection, measurement, analysis, and reporting is a contributing factor to the hinderance of the translation of research into clinical practice.3 Recognition for outcome standardization in pediatric mental health disorders is evolving and there are several initiatives of importance, including the International Consortium for Health Outcomes Measurement (ICHOM), which has developed standardized outcome sets for use in the routine clinical mental health treatment of children and adolescents.4 Similarly, the International Alliance of Mental Health Research Funders5 advocate for use of 1 specific outcome measurement instrument (OMI) in the youth mental health research that they fund. Development of a Core Outcome Set (COS), a minimal set of outcomes that should be measured and reported in clinical trials, has been a solution in other areas of medicine to address heterogeneity in outcome selection and measurement across trials.6 The Core Outcomes and Measures in Pediatric Anxiety Clinical Trials (COMPACT) Initiative will develop a harmonized, evidence- and consensus-based COS that is meaningful to youth and families for use in future trials in pediatric AD.