Objectives: This study aimed to identify the methods used to determine the value of informal care provided to people living with dementia and to estimate the average hourly unit cost by valuation method. Methods: A literature search in MEDLINE Complete, CINAHL, PsycINFO, EconLit, EMBASE and NHS Economic Evaluation Database was undertaken. Following the screening of title, abstract, and full text, characteristics of eligible studies were extracted systematically and analyzed descriptively. The corresponding hourly cost estimates were converted into 2018 US dollars based on purchasing power parities for gross domestic product. Results: A total number of 111 articles were included in this review from 3106 post-deduplication records. Three main valuation methodologies were identified: the replacement cost method (n = 50), the opportunity cost approach (n = 36), and the stated preference method based on willingness to pay (n = 3), with 16 studies using multiple methods and 6 studies not specifying the valuation method. The amount of informal care increased as the condition of dementia progressed, which was reflected in the cost of informal care. The average hourly unit cost used to value informal care was US $16.78 (SD = US $12.11). Although the unit cost was approximately US $15 per hour when using the opportunity cost method and US $14 when using the stated preference method, the highest unit cost was obtained when using the replacement cost method (US $18.37, SD = US $13.12). Conclusions: Although costs of informal care should be considered when undertaking an economic evaluation or estimating the overall costs of dementia from a policy and priority-setting perspective, further research into applying consistent approaches to valuation is warranted.