Background and Objectives: Caring for persons with dementia is a heavy burden for informal caregivers. This study aimed to appraise the economic evidence of interventions supporting informal caregivers of people with dementia. Methods: Literature was searched, and trial-based studies evaluating the costs and effects of interventions supporting informal caregivers of people with dementia were included. Cost data were analyzed from both healthcare and societal perspectives. Random-effects models were used to synthesize cost and effect data, based on mean differences (MDs) or standardized MDs. Results: Of 33 eligible studies identified from 48 588 records, 14 (42.4%) showed net savings in total cost regardless of analytical perspectives. Among 22 studies included in meta-analyses, caregiver-focused psychosocial interventions showed improvements in caregivers’ psychological health (n = 4; standardized MD 0.240; 95% confidence interval 0.094-0.387); nevertheless, the increases in societal cost were significant (n = 5; MD 3144; 95% confidence interval 922-5366). Psychological intervention and behavioral management engaging patient-caregiver dyads showed positive effects on caregivers’ subjective burden, also with increases in total cost. Subgroup analyses indicated that the inclusion of different intervention components, the caregiver characteristics, and the follow-up periods could affect the costs and effects of interventions supporting informal caregivers. Conclusions: Psychosocial interventions directed at informal caregivers and dyad-based psychological and behavioral interventions are effective but also expensive. The use of these interventions depends on the society's willingness to pay. More comprehensive economic evidence of interventions supporting informal caregivers is required, and the design of intervention should focus more on different intervention components, characteristics of patients and caregivers, and healthcare systems.