Background: Nearly 19 million people across OECD countries are living with dementia, and millions of family caregivers are affected by the disease. The costs of informal care are estimated to represent 40–75% of the total dementia cost exceeding formal care time and medical costs. Objective: To conduct a systematic review to evaluate the methodological quality and factors associated with high informal care hours per month that increase societal costs, and to identify what type of interventions may alleviate the entire burden of informal and formal caregiving. Methods: The systematic review was registered at PROSPERO (15.12.2020). A search in Medline, Embase, PsycINFO, and web of science for observational studies, cost-effectiveness, and cost of illness (COI) analyses on resource utilization in dementia (RUD) was conducted on 1 December 2020. Our inclusion criteria included a requirement that studies had to use the original RUD, RUD-FOCA or RUD lite in terms of hours or days per month, and costs as primary or secondary outcome, OECD countries, within the last 20 years and a sample population comprising persons with dementia (PwD) ≥65 years and their caregivers. We followed the PRISMA, GRADE, PICO guidelines and Drummond criteria to assess the methodology and quality of the studies. Results: Of 307 studies, 26 cross-sectional and 3 longitudinal cohort studies were included in the analyses. Two studies had a randomized controlled trial (RCT) design. The methods and cost categories in each study varied widely. Disease severity, caregiver factors, and behavioural and psychological symptoms of dementia (BPSD) were associated with high informal care hours and societal cost. One RCT found no effect of a non-pharmacological intervention on informal care hours, yet another RCT found a cost-effective impact of an in-home respite care programme reducing informal care burden and costs. Conclusion: The divergent use of the RUD components within included studies encourage more harmonized analyses. There are only two RCTs on RUD, one of which shows a significant treatment effect. Larger sample sizes and longer follow-up periods are required in future RCTs with dedicated focus on cost-enhancing and resource intensive factors such as disease severity and BPSD. Novel interventions must diversify between caregiver and PwD groups. PROSPERO registration: CRD42021226388.