INTRODUCTION: Weight stigma and internalised weight bias are associated with poor mental, social and physical health. Weight-neutral approaches prioritise well-being and sustainable health behaviours. However, the feasibility and acceptability of weight-neutral interventions remain uncertain. METHODS AND ANALYSIS: Weight-Neutral Health Intervention (WIN) is an investigator-initiated single-arm feasibility study enrolling 56 adults with body mass index ≥30 kg/m2 in the Capital Region of Denmark. The study investigates a codesigned weight-neutral health intervention. The 6-month intervention comprises 1 preparatory session and 11 group sessions led by trained practitioners, focusing on intuitive eating, body acceptance and self-compassion; optional components include support-network events, up to three individual online sessions and access to 'size-inclusive yoga' and 'body competence' courses. The primary feasibility outcome is follow-up completion. Recruitment proportion and adherence are secondary feasibility outcomes. These will be assessed using a set of predefined 'traffic-light' stop/go progression criteria. Exploratory feasibility outcomes include data completeness for other outcomes and participant engagement with the intervention. Exploratory clinical outcomes include questionnaire data (quality of life, depression, weight bias internalisation, eating behaviours, self-esteem, body image, stress and life satisfaction), clinical measures (weight, heart rate and blood pressure), biomarkers (blood samples and hair cortisol), 7-day actigraphy (physical activity and sleep) and serious adverse events. Qualitative interviews, focus groups and fieldnotes will be used to explore acceptability and contextual factors. If progression criteria are met, the study will inform the design of a pragmatic, multicentre, randomised trial. The exploratory outcomes will inform outcome selection, setting, sample size and procedures. ETHICS AND DISSEMINATION: Approved by the Regional Ethics Committee of the Capital Region of Denmark (H-25013213). Results will be disseminated through peer-reviewed publications, conferences and public platforms. TRIAL REGISTRATION NUMBER: NCT06922630.