BACKGROUND It is now universally acknowledged that climate change constitutes a major threat to human health. At the same time, some of the measures to reduce greenhouse gas emissions, so-called climate change mitigation measures, have significant health co-benefits (e.g., walking or cycling more; eating less meat). The goal of limiting global warming to 1,5° Celsius set by the Conference of the Parties to the United Nations Framework Convention on Climate Change in Paris in 2015 can only be reached if all stakeholders, including households, take actions to mitigate climate change. Results on whether framing mitigation measures in terms of their health co-benefits increases the likelihood of their implementation are inconsistent. The present study protocol describes the transdisciplinary project HOPE (HOuseholds' Preferences for reducing greenhouse gas emissions in four European high-income countries) that investigates the role of health co-benefits in households' decision making on climate change mitigation measures in urban households in France, Germany, Norway and Sweden. METHODS HOPE employs a mixed-methods approach combining status-quo carbon footprint assessments, simulations of the reduction of households' carbon footprints, and qualitative in-depth interviews with a subgroup of households. Furthermore, a policy analysis of current household oriented climate policies is conducted. In the simulation of the reduction of households' carbon footprints, half of the households are provided with information on health co-benefits of climate change mitigation measures, the other half is not. Households' willingness to implement the measures is assessed and compared in between-group analyses of variance. DISCUSSION This is one of the first comprehensive mixed-methods approaches to investigate which mitigation measures households are most willing to implement in order to reach the 1,5° target set by the Paris Agreement, and whether health co-benefits can serve as a motivator for households to implement these measures. The comparison of the empirical data with current climate policies will provide knowledge for tailoring effective climate change mitigation and health policies.