The article explores the testament of Stanisław Tarnowski, a Wieliczka mine clerk, and the testator’s biography. The testament, a previously unexplored source available in the Central Archives of Historical Records, can help in reconstructing Tarnowski’s life. The data from the testament were supplemented with information from other sources, for instance the Councillor book of the town of Warsaw. Stanisław Tarnowski came from moderately rich gentry from Stara Nieszawa. In 1505 he enrolled at Cracow University, where he got the degree of bachelor of liberal arts; he also studied at the Medical College, but did not graduate. Since 1509 he worked as a clerk in the salt mine in Wieliczka; in 1518 by the order of the mine supervisor, Jan Boner, he prepared the first part of the document that is now known as A description of the Cracow salt mines, being also responsible for the editing of the whole text. In 1518 he left Cracow, moving to Warsaw, where he became the town’s citizen in 1521, with most illustrious members of the patriciate being his guarantors. He died soon after that. Tarnowski left a testament containing an extensive list of immovable properties and a list of people connected with him in some way. An analysis of the list of people mentioned in the testament as legatees or executors indicates that Tarnowski’s connections with Warsaw must have been much more stable and long-lasting than it is reflected in other sources. Attaining the status of the town’s citizen by the nobleman connected with salt trade can be considered as the culmination of his career, although it can be supposed that he would have achieved even more if not for his early death. Tarnowski’s last will brings interesting data on both the affluence of those who aspired to the patriciate of Warsaw and the broad horizons of this group, which are evident from bequeathing significant sums to particular charitable institutions. The probate inventory, especially the list of garments, is particularly valuable as it can be confronted with iconographic sources. It indicates clearly that Tarnowski attached great significance to his garments, which allows a historian to look at him from a fresh and very interesting perspective.