Background <p>This research outlines the development and validation of the Alimetry® Gut-Brain Wellbeing Survey-Youth Version (AGBW-Y), a novel tool for assessing mental health in young people with chronic gastroduodenal symptoms aged 12–17&#xa0;years.</p> Methods <p>In Phase 1, global feedback was gathered from 19 pediatric clinicians in the gastroenterology field and 33 young people over multiple rounds to make the adult AGBW Survey more age-appropriate for young people. In Phase 2, rigorous psychometric testing was conducted in a sample of 128 patients aged 12–17&#xa0;years with chronic gastroduodenal symptoms, using an anonymous survey.</p> Results <p>Based on the feedback from Phase 1, an interdisciplinary team of experts improved the survey’s language and usability for young people to enhance the scale’s clarity, acceptability, and face and content validity. The final AGBW-Y comprises a patient preface, 10 closed-ended questions, and an open-ended question. It assesses general mental health, alongside subscales of depression, stress, and anxiety. Phase 2 demonstrated excellent psychometric properties of the scale, including high internal consistency reliability (<i>α</i> = 0.91 for the total scale; <i>α</i> = 0.75–0.85 for subscales) and strong convergent, divergent, and concurrent validity with large effect sizes.</p> Conclusions <p>The AGBW-Y is a brief, reliable, and valid tool to assess mental health in young people aged 12–17&#xa0;years with chronic gastroduodenal symptoms. This novel scale was developed through rigorous co-design with clinicians and young people, ensuring it is contextually relevant and clinically impactful. The AGBW-Y complements existing physiological assessments, enabling evaluations that can guide psychological referrals, support multidisciplinary care, and evaluate treatment outcomes.</p> Graphic abstract <p></p>