BackgroundMental health problems are common among people with diabetes. However, evidence-based strategies for the prevention and early intervention of emotional problems in people with diabetes are lacking. Our aim is to assess the real-world effectiveness, cost-effectiveness, and implementation of a Low-Intensity mental health Support via a Telehealth Enabled Network (LISTEN), facilitated by diabetes health professionals (HPs).MethodsA hybrid type I effectiveness-implementation trial, including a two-arm parallel randomised controlled trial, alongside mixed methods process evaluation. Recruited primarily via the National Diabetes Services Scheme, Australian adults with diabetes (N= 454) will be eligible if they are experiencing elevated diabetes distress. Participants are randomised (1:1 ratio) to LISTEN—a brief, low-intensity mental health support program based on a problem-solving therapy framework and delivered via telehealth (intervention) or usual care (web-based resources about diabetes and emotional health). Data are collected via online assessments at baseline (T0), 8 weeks (T1) and 6 months (T2, primary endpoint) follow-up. The primary outcome is between-group differences in diabetes distress at T2. Secondary outcomes include the immediate (T1) and longer-term (T2) effect of the intervention on psychological distress, general emotional well-being, and coping self-efficacy. A within-trial economic evaluation will be conducted. Implementation outcomes will be assessed using mixed methods, according to the Reach, Effectiveness, Adoption, Implementation, and Maintenance (RE-AIM) framework. Data collection will include qualitative interviews and field notes.DiscussionIt is anticipated that LISTEN will reduce diabetes distress among adults with diabetes. The pragmatic trial results will determine whether LISTEN is effective, cost-effective, and should be implemented at scale. Qualitative findings will be used to refine the intervention and implementation strategies as required.Trial registrationThis trial has been registered with the Australian New Zealand Clinical Trials Registry (ACTRN: ACTRN12622000168752) on 1 February, 2022.Supplementary InformationThe online version contains supplementary material available at 10.1186/s13063-023-07338-5.