Understanding the processes that guide fleet management by corporations is key to assessing the potential role corporations could play in the transition towards a more sustainable mobility system, and to drawing operational policy conclusions accordingly. Building on the information collected through 44 interviews with decision-makers from 22 large organisations in the Paris region, we reach a much deeper understanding of the fleet management processes of large organisations. We find that the prospects for global optimisation of the corporate car fleet – from the perspectives of both purchase behaviours and daily operations –depend on the solutions that corporations can find to tackle the complexity of the decision-making processes for car fleet acquisition (e.g. through implementing car policies) and the shortcomings of information on fleet use and fleet costs (e.g. through deploying monitoring and tracking technologies). In order to discuss the outlook for electric vehicles and car-sharing services in corporate car fleets, we analyse the specific barriers to, and drivers of, their adoption, and report on some of the ‘best practices’ revealed by our survey.