In the past, the art history of the early modern period focused primarily on the research of works of art, artists, commissioners and collecting. The phenomenon of (art) agents, however, has recently begun to make its way into the field of study focused on European cultural centres. Issues concerning how the artwork is acquired and the role of agents and dealers in the mechanism of art patronage have become more apparent. The results of this quite demanding archival research, in which sociological, politological and economic aspects prevail over the historical interest, can provide us with valuable insights into the issue of patronage in the early modern, art dealing, the network of agents, their competencies and methods of communication, mechanisms of acquiring artworks, transport of the artworks, and patronage strategies. The agents’ letters are able to convey the colourful life of the patrons, the breadth of their interests, an awareness of current events and, last but not least, they provide new findings about individual artworks. In some cases, the letters can reveal the importance of agents who were not just mere executors of the artistic and collecting goals of their patron but who often participated in shaping and giving a character to their artistic and sponsorship activities. The presented study analyses the network of agents of the Olomouc bishop Karl von LichtensteinCastelcorno (1624–1695), primarily focusing on Giovanni (Jean) Petignier, who was located in Rome. This agent mainly followed political and cultural events at the Holy See but occasionally fulfilled the bishop’s wishes in the area of patronage. More than seven hundred surviving letters allows us to follow the acquisitions of individual artworks — mainly albums of prints and books but also the commission of a large painting from Luigi Garzi (1638–1721). The correspondence provides a rich understanding of the relationship between agent and patron and the role agents played during the decision-making process when acquiring specific works of art.