INTRODUCTION: To minimise adverse health events among older adults, physical activity (PA) is considered one of the most fundamental and effective forms of lifestyle. Therefore, an urgent effort to promote a physically active lifestyle among our older adults is needed, in which walking could be a better choice, especially for mass promotion. Besides, the types of PA interventions were also shown to affect their effectiveness on older adults' psychosocial outcomes. Hence, the overall aim of the project is to examine the effectiveness of supervised group-based walking intervention by comparing it with unsupervised group-based walking and unsupervised individual-based walking interventions on improving physical, psychological and social outcomes among older adults in Hong Kong. METHODS AND ANALYSIS: The research will conduct a four-group (supervised group-based, unsupervised group-based walking, unsupervised individual-based, control group), double-blind, randomised control trial, targeting 184 older adults in Hong Kong. The primary outcomes will be measured by participants' changes in resting heart rates, body compositions, resting blood pressures, walking performance, loneliness, perceived social support and PA enjoyment. The results will be analysed using repeated analysis of variance and one-way analysis of covariance, as well as by conducting in-depth interviews with selected participants. Also, the outcomes of the research will be used as references for designing an effective walking operation manual for promoting healthy ageing among older adults in the community. ETHICS AND DISSEMINATION: The current study involves human participants, and the research protocol has been approved by the research ethics committee at Hong Kong Baptist University (Ref: R2022-2023-0013). All participants will be provided with written informed consent to participate. The outcomes of the intervention protocol will be disseminated through manuscript publications. TRIAL REGISTRATION NUMBER: The trial is registered at the ClinicalTrials.gov PRS (Trial ID: NCT05907252; date of first posted: 16 June 2023).