Many climate change mitigation policies face public opposition, especially when they impose visible costs on households and areperceived as unfairly regressive. This country-comparative study examines specific social policy instruments that may help build public support for increasing fossil fuel taxes in Europe. Using multilevel modeling with data from the European Social Survey and the Social Policy Indicators database, we find that higher levels of means-tested social assistance are positively associated with greater public support for fossil fuel taxes. More specifically, means-tested social assistance appears to promote support by reducing self-experienced economic hardship and lessening value conflicts among individuals with strong eco-social values. Policies that raise the minimum income floor in society thus seem crucial for fostering eco-social synergies and strengthening public support for government-led climate action and decarbonization efforts.