Understanding the processes that guide fleet management by corporations is key to assessing the role that corporations could play in the transition toward 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 organizations in the Paris region yields a much deeper understanding of the fleet management processes of large organizations. It was found that the prospects for global optimization of the corporate car fleet—from the perspectives of both purchase behaviors 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). To discuss the outlook for electric vehicles and carsharing services in corporate car fleets, the specific barriers to, as well as drivers of, their adoption are analyzed, revealing some of the best practices.