From the 1930s to the 1950s, Fenner Brockway (1888-1988) and Marceau Pivert (1895-1958), both ‘left-wing’ socialists, were deeply committed to anti-colonialism. Brockway lived mostly in the United Kingdom and Pivert in France, but their involvement was not restricted by national boundaries. Regarding colonial issues, both men conceived of the militant activities they pursued in transnational terms. This was a feature of their distinct internationalist approach of politics. Their relationship was part of a wider European network of militants, and their strife against colonial imperialism was embodied in various collective forms of action. The Brockway–Pivert connection thus illustrates the way two anti-colonialist stances met and interacted on different scales and levels. The ideas, the initiatives and the practices of this specific form of socialist anti-colonialism are at the heart of this chapter.