Background: In dementia care, a large number of treatment decisions are made by family carers on behalf of their family member who lacks decisional capacity; advance care planning can support such carers in the decision-making of care goals. However, given the relative importance of advance care planning in dementia care, the prevalence of advance care planning in dementia care is poor. Aim: To evaluate the effectiveness of advance care planning with family carers in dementia care homes. Design: Paired cluster randomized controlled trial.