The essay concerns the diplomats of King Casimir the Great who traveled as envoys to Avignon, the then papal seat. In fact, every major diplomatic action of the king was preceded by Polish actions in Avignon, where he sought support for his projects. This was especially necessary in the face of the conflict between Poland and the Teutonic Knights over Pomerania. It is therefore understandable that the first royal embassies dealt with religious matters. In this first period, Casimir used experienced diplomats who began their service during the times of Władysław Łokietek. In the 1440s, new men appeared in the royal diplomatic service to replace the previous generation, most of them were clergy, often associated with the royal chancellery and, through their studies abroad, responsible for taking care of the tasks assigned to them. Service in royal diplomacy usually meant a path to promotion in the form of rich benefices.