After the Nazis came to power, Ludwig Werner Kahn emigrated to Switzerland in 1933 and moved to England one year later, where he held the post of Assistant Lecturer in German at University College in London until 1936 and worked as a research assistant at the Warburg Institute.
After emigrating to the USA in 1937, Kahn worked at various American universities, e.g. as a professor at the City College of New York. From 1973-1976 he was the director of the Deutsches Haus at Columbia University in New York; in 1974, he became a member of the Council for Research in the Humanities at Columbia University, New York. Ludwig Werner Kahn published a large number of works, including “Social ideals in German literature: 1770–1830 (New York: Columbia University Press, 1938) and "Literatur und Glaubenskrise" [Literature and the Crisis of Faith] (Stuttgart: Kohlhammer, 1964).
Kahn received several awards for his work. He was a Senior Fulbright Research Fellow at the University of Stuttgart, a Fellow of the John Simon Guggenheim Foundation, and received the Federal Cross of Merit, 1st class. In 2003, Ludwig Werner Kahn presented his written legacy to the German Exile Archive 1933–1945. In a letter dated 2 August 2003, he wrote:

“I am somewhat surprised that the German Exile Archive is interested in my papers, because I did not think that I or my papers were of interest. I had already destroyed some of them [...].”

Ludwig Werner Kahn died in Seattle, Washington, on 4 December 2007. The German scholar's estate contains academic and personal correspondence, including letters from Richard Alewyn, Käte Hamburger, Sol Liptzin (who succeeded Kahn as the Chairman of the Department of German and Slavic Languages at the City College of New York), Kurt Pinthus, Hilde Spiel, Johannes Urzidil and Harry Zohn. The collection also includes personal documents and specimen copies of his academic works.