This study examined the socioeconomic costs of dementia based on the utilization of healthcare and long-term care services in South Korea. Using 2016 data from two national insurance databases and a survey study, persons with dementia were categorized into six groups based on healthcare and long-term care services used: long-term care insurance users with home- and community-based services (n = 93,346), nursing home services (n = 69,895), and combined services (n = 16,068); and long-term care insurance non-users cared for by family at home (n = 192,713), living alone (n = 19,526), and admitted to long-term-care hospitals (n = 65,976). Their direct and indirect costs were estimated. The total socioeconomic cost of dementia was an estimated US$10.9 billion for 457,524 participants in 2016 (US$23,877 per person). Among the six groups, the annual per-person socioeconomic cost of dementia was lowest for long-term care insurance users who received home- and community-based services (US$21,391). It was highest for long-term care insurance non-users admitted to long-term care hospitals (US$26,978). Effective strategies are necessary to promote long-term care insurance with home- and community-based services to enable persons with dementia to remain in their communities as long as possible while receiving cost-efficient, quality care.