Unpaid caregivers of people living with dementia tend to suffer mental health problems as a result of the negative effects associated with the care tasks. Thus, psychosocial interventions for this population group are necessary. iSupport is an online support program for caregivers that was created by the World Health Organization. Objective: To describe the design of a randomized clinical trial to measure the efficacy of the iSupport-Brasil version on caregivers’ mental health and well-being. Methods: The participants will be randomized into Intervention Group (IG) (n=195) and Control Group (CG) (n=195). For three months, the IG will access the iSupport-Brasil platform, the CG will enter the electronic page of the Brazilian Alzheimer’s Association, and both groups will be emailed the preliminary version of the “Guia de cuidados para a pessoa idosa” e-book (a guide to providing care to the elderly) from the Ministry of Health. The data will be collected at three moments: baseline, and three and six months after the beginning of the intervention. Results: It is expected that it will be possible to provide diverse validity evidence about iSupport-Brasil as an online and free intervention alternative, as a preventive means and as a way to promote mental health among caregivers of people living with dementia. Conclusion: Through the evaluation protocol of this randomized clinical trial on the effects of the iSupport-Brasil program, it may become a reference for countries that plan to adapt and improve the iSupport program using digital health solutions.