Besides his activities as a theoretical physicist, the Belgian Léon Rosenfeld cultivated and showed a lively concern for history of science since his student years. This paper is a study of his publications, correspondence and other endeavours in history of science, mainly during the early Cold War period, in order to explore his essentially Marxist views on science and society and how they differed from those of other Marxists scholars, most notably John D. Bernal and Boris Hessen.