Aims: This study aims at identifying the health effects of a strength‐based intervention on family caregivers of persons with dementia and to explore the underlying mechanism. The perception of family caregivers on the strength‐based intervention will also be explored. Design: This sequential mixed‐method study comprises a double‐blind randomized controlled trial and a descriptive qualitative study. Methods: A group of 372 family caregivers of persons with dementia will be recruited from community settings. They will be randomized to receive the strength‐based intervention or a dementia education program. Based on Antonovksy's theory of salutogenesis, the strength‐based intervention integrates skills of narrative therapy and empowerment strategies. It comprises 14 weekly group‐based sessions and two bi‐weekly follow‐up telephone calls. The education program serves as the control intervention. Validated instruments are used to measure sense of coherence, coping, caregiver burden, and health‐related quality of life at baseline, 14 weeks, and 22 weeks. Mixed‐effects models and path analysis will be used to identify the treatment effect and the mediating mechanism. A subsample of 30 caregivers who report differential changes in the health outcome will be engaged in qualitative interviews. The study was funded in 2017. Discussion: This study marks the first attempt to adopt a theory‐driven strength‐based approach to improve the health outcomes of family caregivers of persons with dementia. The stringent and comprehensive evaluation will inform its effects and the underlying mechanism. Impact: This study will have important theoretical and public health implications. Theoretically, the study will enhance understanding of Antonovsky's theory of salutogenesis by examining the modifiability of sense of coherence and the way it enhances health‐related outcomes. In terms of public health implications, the strength‐based intervention focusing on optimizing the inner strength can provide a new paradigm to promote the adjustment of family caregivers of persons with dementia. Trial Registration: This project was registered in the Clinical Trials Registry of the Centre for Clinical Research and Biostatistics (registration number: CUHK_CCRB00551; date registered: 6 April 2017).