This review aims to synthesise evidence about interventions to reduce anxiety symptoms in school-aged children with autism spectrum disorder (ASD). While clinical studies will not be excluded per se, this review seeks to move beyond interventions that are relevant only for clinical practice and care in clinical settings and prioritise studies that draw out implications for school-aged children that will help their functioning in real-world settings such as school and the home. To achieve this aim, the review will employ a mixed-methods systematic review which can accommodate the anticipated diverse types of available studies. These studies are likely to use quantitative methods such as quasi-experimental, mixed-methods randomised control trial approaches as well as qualitative methods such as action-research and case-study designs. This publication outlines the methodology which will be used in the systematic review and covers the criteria for inclusion and exclusion of studies in the review, the search strategy to be used for identification of relevant studies, the bibliographic databases and other sources used for searching, the data collection process including the selection process and data synthesis and analysis, and the timeframe for this project.