The article aims to analyse the main stages of the political thought of Rudolf Rocker (1873-1958), an important figure in the history of twentieth-century anarchism. During his long life, Rocker faced the meaningful transformations caused by the First World War, the Russian Revolution, the rise of the fascist regime in Italy and the Nazi regime in Germany, the Second World War and the beginning of the Cold War. His political approach changed depending on the historical contexts, moving from the anarcho-syndicalism of the 1920s/1930s to the libertarian revisionism of the 1940s/1950s. The article examines his most important writings, especially Nacionalismo y cultura (1937), and numerous articles published in the anarchist press from 1919 to 1953.