Background Informal caregivers of persons living with dementia have an increased risk of adverse mental health effects. It is therefore important to systematically summarize published literature in order to find out which mental health interventions generate effective support for informal caregivers of persons living with dementia. The objective of this study is to conduct a systematic review of intervention content, effectiveness and subgroup differentiation of mental health interventions for informal caregivers of persons with dementia living at home. Method We searched four electronic databases (PubMed, PsychINFO, Scopus and CINAHL) and included only methodically high-quality randomized controlled trials (RCTs), published in English or German language between 2009 and 2018. The intervention programmes focused on mental health of family caregivers. A narrative synthesis of the included studies is given. Results Forty-eight publications relating to 46 intervention programmes met the inclusion criteria. Burden, depression and quality of life (QoL) are the predominant parameters that were investigated. Twenty-five of forty-six interventions (54.3%) show positive effects on at least one of the outcomes examined. Most often, positive effects are reported for the outcome subjective burden (46.2%). Only six studies explicitly target on a certain subgroup of informal dementia caregivers (13%), whereas all other interventions (87%) target the group as a whole without differentiation. Conclusion The most beneficial results were found for cognitive behavioural approaches, especially concerning the reduction of depressive symptoms. Besides this, leisure and physical activity interventions show some good results in reducing subjective caregiver burden. In order to improve effectiveness, research and practice may focus on developing more targeted interventions for special dementia informal caregiver subgroups.