IntroductionPhysical activity (PA) and replete nutritional status are key to maintaining independence and improving frailty status among frail older adults. In response to the COVID-19 pandemic, healthcare has increasingly turned to virtual modes of delivery and there is interest in the use of trained volunteers to deliver PA and nutrition interventions. We aim to evaluate the feasibility and acceptability of training hospital volunteers to deliver an online intervention, comprising exercise, behaviour change and nutrition support, to older people with frailty after discharge from hospital.MethodsWe will use a quasi-experimental mixed methods approach. Hospital volunteers (n=6) will be trained to deliver an online, 3-month, multimodal intervention to frail (Clinical Frailty Scale ≥5) adults ≥65 years (n=30) after discharge from hospital. Feasibility will be assessed by determining the number of volunteers recruited, trained and retained at the end of the study; the proportion of intervention sessions delivered; participant recruitment, retention and adherence to the intervention. To determine the acceptability of the intervention, interviews will be conducted among a purposive sample of older adults, and volunteers. Secondary outcomes will include physical function, appetite, well-being, quality of life, anxiety and depression, self-efficacy for managing chronic disease and PA. Outcomes will be measured at baseline, 3 months and 6 months.AnalysisDescriptive statistics will be used to describe feasibility and adherence to the intervention. Secondary outcomes at baseline will be compared at 3 and 6 months. Interviews will be transcribed verbatim and analysed using thematic analysis.Ethics and disseminationHealth Research Authority ethical approval was obtained on 30 May 2022 (reference: 22/WA/0155). Results will be disseminated through peer-reviewed journal articles, volunteer organisations, National Health Service communication systems and social media platforms. A toolkit will be developed to facilitate roll out of volunteer training.Trial registration numberNCT05384730.