The aim of the article is to present and discuss the post-war achievements of Augustyn Steffen (1901–1992), a researcher of Warmian folklore. Little is known about his publications from before World War II, recording dialectal literature, and almost nothing is known about how he promoted the knowledge of the Polish language, Warmian dialect and the region of Warmia and Mazury after the war, while in exile, in Polish and emigration periodicals. In addition to analyzing the content of selected studies by the linguist, the article cites the results of his research on two important manuscripts from centuries ago: the Polish-Latin dictionary published by Steffen, entitled “Tridentine glossary” and the written in Old Polish language: “Wilkierz budnicki”.