Recent scholarship has focused on how coordination mechanisms are implemented by public sector organizations, thereby paying attention to coordination as a process. This article studies the coordination process that resulted in the implementation of the interministerial financial information system of the French central state—named Chorus. Chorus is a case of an unlikely coordination process rolled out in the non-conducive context of the French Napoleonic Administration. Chorus aimed at connecting all ministries’ administrative services to a shared information system, while ministries were previously using their own systems and applications. Based on the literature on mechanisms of coordination, and focusing on the role of existing institutions and the actors involved in the coordination process, the analysis has two main results. First, AIFE—“Agence pour l’informatique financière de l’État”, the agency in charge of the implementation of Chorus—steered the process by developing a stepwise network-based interministerial strategy. Second, the coordination steered by AIFE resulted in a transformative change of the French state's financial and accounting structures through a layering process of change. Thereby, the article contributes to the empirical analysis of public administrations’ recent changes toward increased coordination at the central level by studying recent reforms in France and their outcomes.