Karl Rühmann spent his childhood in Yugoslavia. As a teenager, he emigrated to the United States, but after a few years he returned to Europe to study German studies, Hispanic studies, and general literary studies in Zagreb and Münster.After completing his studies, he initially worked as a language teacher in Switzerland and Denmark before moving into the publishing industry in the late 1990s.

In 2006, he founded the licensing agency "books&rights" as well as the consulting agency "Plot & Story Rühmann." He also taught publishing studies and translation at SAL, the School of Applied Linguistics.

Karl Rühmann lives in Zurich as a freelance writer and literary translator. Until 2018, he mainly wrote children's books and radio plays; since then, he has focused primarily on novels for adults. His novel Der Held was nominated for the Swiss Book Prize in 2020. In 2025 Matija Katun und seine Söhne was published (both rüffer & rub).