<p>Brain science research targeting neurodevelopmental disorders has rapidly advanced in recent years. Although findings from these studies could potentially serve as objective indicators for future screening and diagnosis, researchers may encounter ethical challenges when returning results to participants and their legal guardians, such as family members. Furthermore, no established guidelines exists for returning results in this field, either in Japan or internationally. This study aimed to identify the ethical considerations associated with returning results in brain science research on neurodevelopmental disorders and to develop a protocol for doing so. The authors held regular meetings to discuss ethical issues and conducted a comprehensive search for relevant guidelines and literature. Databases such as PubMed, Igaku Chuo Zasshi, CiNii, and Google Scholar were searched for prior studies. Additionally, we referenced and manually searched genetic research literature and guidelines, as ethical considerations related to returning results in genetic and brain science research share commonalities, and the former has already advanced discussions on these issues. Key ethical concerns identified include the certainty of the results, the psychological burden of returning results, and the decision-making process. Researchers should verify the accuracy of results and, based on this, decide whether and how to return them. It is crucial to tailor explanations to the unique characteristics of neurodevelopmental disorders. Moreover, supporting participants in making autonomous decisions while respecting the authority of their legal guardians is essential.</p>