This study aims to evaluate the impacts of an advance care planning (ACP) programme "Have a Say" for persons with early stage dementia (PWEDs) or mild cognitive impairment and their family caregivers in the community. A randomized controlled trial with repeated blinded outcome assessment will be conducted to assess the effects of an ACP programme on dyads of PWEDs or persons with MCI and their family caregivers recruited from elderly community centres. Individuals who have a clinical diagnosis of any form of dementia at the early stage or have a Global Deterioration Score (GDS) 3 or 4 will be eligible to this study. Participants in the experimental group will receive a 4-session ACP programme. It includes an educational component, guided reflection and ACP discussion through a series of group-based activity and dyadic discussion delivered by trained ACP facilitator and guided by an ACP booklet. Dyads of participants will be provided with information about the trajectory of dementia, their future healthcare needs and caring options. Their values and care preferences on future care will be elicited in a consistent manner. They will be supported to have an individualized ACP discussion. Individuals assigned to the control group will receive attention-control health talks. The primary study outcome is the ACP engagement level of PWEDs. Secondary outcome is the dyadic concordance on end-of-life care preference. Adverse outcomes such as depression and caregivers' burden will also be evaluated. Data collection will be conducted at baseline, immediately after, one month and three-months after the intervention.