Objectives: To compare online cognitive-behavioral therapy (CBT) with and without telephone support respectively to online psychoeducation in a randomized controlled trial (RCT) in caregivers of people with dementia with mild anxiety or depression. Methods: Three-arm parallel-group RCT comparing online CBT with and without telephone support respectively to online psychoeducation. Online study with caregivers of people with dementia. The primary outcome measure was mental health measured by General Health Questionnaire–12 (GHQ-12) at 26 weeks.