A successful decarbonization of the European Union, coupled with a high integration of renewable energy and ambitious targets for energy efficiency, can only be reached with a significant contribution from transport. This sector currently represents a quarter of the total greenhouse gas emissions and is shifting from fossil fuels to alternative energy carriers and propulsion systems. Decarbonizing this sector can follow multiple pathways, each having different costs, impacts and implications for the other sectors (industry, residential and services). This paper focuses on the impact of different decarbonization paths in the mobility sector on the whole energy system of a country. The hourly and monthly resolution model named EnergyScope was used and applied to three European countries with different characteristics, namely France, Germany and Switzerland. Their energy resources, demands and policies are strongly different, which has an impact on the preferred decar- bonization pathway to follow, and on its final costs and environmental impacts. Regardless of the case study, the most cost- and energy-efficient pathway to decarbonize road and rail mobility is through a heavy electrification, with short-range electric vehicles and buses for local mobility, and either hy- drogen or long-range electric vehicles for long-distance. The most cost-optimum vehicle fleet depends strongly on the projected costs of fuel cell and batteries in the upcoming year, as well as on the wind and solar energy potential. Large-scale deployment of biofuels seems improper for road transport because of the small potentials for sustainable biomass harvesting and the high installation costs of direct air capture, but may be the only viable solution for aviation.