IntroductionFew clinical trials have examined the effects of home-based exercise programmes on health-related quality of life (HR-QoL) in older adults with frailty. Radio-Taiso is the most famous exercise programme in Japan. A home-based Radio-Taiso exercise programme may serve as an accessible, scalable and sustainable care intervention for older adults with frailty. The primary aim of this trial is to test whether older adults with frailty who are prescribed our home-based Radio-Taiso exercise programme will receive greater benefits for HR-QoL compared with those who are not prescribed the exercise programme. Potential mechanisms underlying the effectiveness of the programme and the effects of the programme on daily lifestyle will also be investigated.Methods and analysisThis assessor-blind randomised controlled trial will be conducted at the Tokyo Metropolitan Institute of Gerontology (TMIG) in Itabashi-ku, Tokyo, Japan. From April to May 2022, 226 older adults with prefrailty or frailty according to the revised Japanese version of the Cardiovascular Health Study criteria will be included from a large database. After a baseline assessment in June 2022, participants will be randomly assigned to the intervention (home-based Radio-Taiso exercise and nutrition programme) or control (nutrition programme) groups at a 1:1 ratio. After intervention completion, a follow-up assessment will be conducted in September 2022. The primary outcome is the change in the mental domain of HR-QoL assessed using SF-36. Secondary outcomes include physical and role/social domains and subscales of HR-QoL, frailty phenotype, physical fitness, posture, cognition, exercise self-efficacy, depressive symptoms, brain-derived neurotrophic factor, social network, habitual energy intake, physical activity and sleep conditions.Ethics and disseminationThe Research Ethics Committee of TMIG has approved the research protocol. This trial will be conducted in accordance with the principles of the Declaration of Helsinki. The findings will be presented at international academic conferences and published in peer-reviewed international journals.Trial registration numberUMIN000047229.