Background: The prevalence of dementia is currently set to rise to 1.7 million by 2040, with associated costs estimated at £90 billion. Given its substantial impact on quality of life (QoL) and the growing societal and financial burden, identifying efficient approaches to dementia support is a key policy priority. Current policy direction emphasises a shift toward community-based models of care; however, economic evidence is required to determine whether such approaches can improve outcomes while representing cost-effective use of limited healthcare resources. This study presents a cost-effectiveness analysis of the Sage House Model, a community-based dementia support intervention integrating NHS diagnostic services, third-sector provision, and local partnerships within a single hub. Methods: A preliminary cost-effectiveness analysis was conducted using a natural experimental design comparing individuals with dementia accessing the Sage House Model (n = 65) to those receiving usual care (n = 153). Health-Related Quality of Life (HRQoL) and health and social care utilisation were collected over a three-month period and valued from a health and social care perspective. Incremental costs and outcomes were estimated to assess cost-effectiveness. Results: The Sage House Model was associated with lower incremental costs and higher incremental QALYs compared to usual care over the three-month time horizon and was likely to be cost-effective, with a 72.2% probability at a £20,000 willingness-to-pay threshold and 74.7% at £30,000 per QALY. Conclusions: These findings provide preliminary evidence that community-based dementia support approaches, such as the Sage House Model, may represent a promising strategy for improving outcomes alongside more efficient use of health and social care resources, and therefore warrants larger scale investigation.