During the Revolution, the legal status of diplomacy underwent an unprecedented change. Diplomatic service was no longer a royal honor, reserved for a minority of the noble elite. It became a public service, the province of citizens who had demonstrated their “virtues” and “talents.” As imprecise as these two criteria were, they permitted a profound renewal of the diplomatic personnel and contributed to an enduring redefinition of the purposes of the tool of diplomacy. This article focuses on the logics, mechanisms, and stages of this evolution by undertaking an analysis of the process and the criteria of recruitment of officials sent to posts or on missions abroad. Never defined in the text of a law, these criteria can only be identified by bringing together the letters of candidates for recruitment or promotion in the diplomatic corps, with the selection procedures put in place by different institutional organs. From among the criteria used by the Ministry, the deputies, and applicants, multiple models of “diplomacy” emerge. However, the criteria of expertise took precedence. During the Revolution, then, the changes to the diplomatic apparatus did not follow a simple logic of “democratization” or “politicization.” They responded to a demand for professionalization, which the application letters, letters of recommendation, and nominations allow us to observe at once in its methods and its limits.