Background: There is increasing interest in assessing the effects of interventions on older people, people with long-term conditions and their informal carers for use in economic evaluation. The Adult Social Care Outcomes Toolkit for Carers (ASCOT-Carer) is a measure that specifically assesses the impact of social care services on informal carers. To date, the ASCOT-Carer has not been preference-weighted. Objectives: To estimate preference-based index values for the English version of the ASCOT-Carer from the general population in England. Methods: The ASCOT-Carer consists of 7 domains, each reflecting aspects of social care-related quality of life in informal carers. Preferences for the ASCOT-Carer social care-related quality of life states were estimated using a best-worst scaling exercise in an online survey. The survey was administered to a sample of the general adult population in England (n = 1000). Participants were asked to put themselves into the hypothetical state of being an informal carer and indicate which attribute they thought was the best (first and second) and worst (first and second) from a profile list of 7 attributes reflecting the 7 domains, each ranging at a different level (1-4). Multinomial logit regression was used to analyze the data and estimate preference weights for the ASCOT-Carer measure. Results: The most valued aspect by English participants was the 'occupation' attribute at its highest level. Results further showed participants rated having no control over their daily life as the lowest attribute-level of all those presented. The position of the 7 attributes influenced participants' best and worst choices, and there was evidence of both scale and taste heterogeneity on preferences. Conclusion: This study has established a set of preference-based index values for the ASCOT-Carer in England derived from the best-worst scaling exercise that can be used for economic evaluation of interventions on older individuals and their informal carers.