Background: Interventions in health care often not only have an effect on patients, but also on their informal caregivers. Caregiving can have a profound impact on the health and wellbeing of carers. Ignoring these spillovers in economic evaluations risks labelling interventions mistakenly as cost-effective, at the expense of informal caregivers. Objective: This paper investigates willingness-to-accept (WTA) values for an hour of informal care, corrected for positive and negative impacts of informal care, to facilitate the inclusion of informal care hours on the cost side of economic evaluations without double-counting spillover effects. Methods: A discrete choice experiment (DCE) was conducted among a representative sample of the adult population in the Netherlands (n = 552) in September 2011. An experimental design minimizing the D-error was used to construct choice sets with two unlabelled alternatives with the attributes 'hours caregiving', 'monetary compensation for caregiving' and seven impacts of caregiving. To operationalize the random utility model, we used a panel mixed multinomial logit (MMNL) parameter model. For calculation of WTA, we used both population-level parameters and individual-level parameters. Results: The mean WTA for an additional hour of informal care, corrected for positive and negative impacts of informal care, was €14.57. The signs of the coefficients were all in the expected directions. Conclusions: This study reports a preference-based monetary value for informal care, corrected for other impacts. This valuation facilitates the inclusion of informal care hours on the cost side in economic evaluations without double-counting any spillover effects included on the effects side.