Purpose <p>Sensory integration therapy is used widely despite an inconsistent evidence base. To overcome the limited availability of high-quality research, Ayres Sensory Integration (ASI) was manualized and a revised fidelity measure was developed following the identification of the principles of ASI^®. The aim of this systematic review is to examine the proximal and distal effects of interventions in studies that explicitly reported the use of or adherence to the process elements of the fidelity measure.</p> Methods <p>A systematic review was conducted following PRISMA guidelines. Following the screening of 2561 titles and abstracts, full-text screening was conducted. Appraisal was conducted on the quality of experimental studies and Goal Attainment Scaling (GAS) administration.</p> Results <p>Ten studies that involved children younger than 10&#xa0;years were identified. Positive outcomes were reported in higher risk of bias studies and case studies. Only four studies were rated as having a low risk of bias. No study directly measured both proximal and distal outcomes, used blind assessors, and reported intervention fidelity data. Mixed results were reported in low risk of bias studies. The quality of the GAS used was poor in studies where positive outcomes were identified.</p> Conclusion <p>There is limited current evidence to support the positive effect of interventions adhering to the ASI fidelity measure. Recommendations include (a) using practices or strategies that are supported by a higher level of evidence to explicitly address needs and functional goals prioritized by individuals and their families, and (b) modifying environments to support individuals who present with sensory difficulties.</p>