This paper presents the first complete edition of Thomas Seget’s album amicorum, held at the Vatican Library (Cod. Vat. Lat. 9385). A friend of Galileo and Kepler, Seget was a background figure who played an important role within the learned world of the late Renaissance. Largely invisible in modern scholarship, figures like Seget played significant functions as cultural intermediaries and international political agents, thus occupying a new and critical position within the learned world of early modern Europe. Seget’s album amicorum offers a unique collection of autograph notes (including Galileo, Sarpi, Lips, Ortels, Pinelli, Welser, De Put, Querenghi, Fabri de Peiresc, Pignoria and Possevino, to mention but a few) which allows us to reconstruct the web of connections Seget managed to weave on his way from Leuven to Padua, as well as during the years he spent in Italy within Pinelli’s circle. Although the album stops at the end of 1600, Seget’s networking activity continued, with ups and downs, throughout his life, and is reconstructed here by way of published and unpublished documents. The paper comprises an Introduction, with a biography of Seget; a Note to the text, providing key elements to understand the role of the album amicorum in the sixteenth and seventeenth centuries, as well as presenting the criteria of the present edition; a critical edition of Seget’s album; and three appendixes: a chronological table of the entries in the album; the transcription of entries by Seget in some of his friends’ albums; and the transcription of a few hitherto unpublished manuscript documents with information about Seget’s life and whereabouts.