Abstract Background Opportunities for prevention are frequently missed in hospital settings despite contact with individuals at increased risk of chronic disease. Hospital-embedded services may enable opportunistic interventions within routine secondary care, through behavioural change frameworks such as Making Every Contact Count (MECC). However, evidence on their uptake, inclusivity and value remains limited. Methods A retrospective service evaluation of a hospital-based prevention and wellbeing service (Here for Health, Oxford University Hospitals NHS Foundation Trust) was done between 2024-2025. Routine data were extracted and analysed to describe activity, delivery modes, reasons for referral, and referral patterns. Service user sociodemographic characteristics were compared with local population benchmarks. A cost–utility and return-on-investment analysis was conducted using a MECC value-for-money model. Results A total of 5,255 encounters were delivered across inpatient, outpatient, staff and community pathways over the evaluation period, predominantly within acute hospital settings (95%). Service users were mostly aged 45–74 years (61%). There was higher representation from non-White ethnic groups (29%) and residents of more deprived neighbourhoods (22%) compared with local sociodemographic indicators. Smoking (49%), weight management (21%) and blood pressure (8%) were the most common reasons for referral. Consultations addressed multiple topics (mean 1.7/encounter). 22% of encounters resulted in onward referral. The model estimated a social return of £4/£1 invested, with 34 QALYs generated at £8,307/QALY. Discussion This evaluation of a large UK-based hospital prevention service demonstrates scalable delivery, equitable reach and cost-effectiveness. Similar models to embed behaviour change support across NHS healthcare pathways may also offer significant public health value.