Public long-term care (LTC) systems are common across Organisation for Economic Co-operation and Development countries and they provide services to support people experiencing difficulties with their activities of daily living. This study investigates the marginal effect of changes in public LTC expenditure on care-related quality of life (CRQoL) in England. The public LTC programme for people aged 18 or older in England is called Adult Social Care (ASC) and it is provided and managed by local authorities. We collect data on outcomes and characteristics of public ASC users, and on public ASC expenditure and characteristics of local authorities across England in 2017/18. We employ an instrumental variable approach using conditionally exogenous elements of the public funding system to estimate the effect of public ASC expenditure on users’ CRQoL. Our findings show that increasing public ASC expenditure by £1,000 per user generates 0.0031 additional CRQoL. These results suggest that public ASC is effective in increasing users’ quality of life but only to a relatively small extent. Combined with other findings on the effect of LTC expenditure on mortality, this study can inform policy makers in the UK and around the world about whether social care provides good value for money