Scandinavia (Denmark, Norway and Sweden) is frequently seen as a democratic ‘island of peace’ in international politics and the three states are seen as ardent supporters of an ‘international community’ under the umbrella of the United Nations as well as its predecessor, the League of Nations. This article seeks to challenge this idealised, unitary conception of Scandinavian peace politics by exploring how different strands of internationalism, as transnational phenomena, developed from the outbreak of the First World War until the three states became members of the League. Initially, that development was more or less independent of official foreign policy. The article explains how and to what degree new internationalist ideas were eventually merged with traditional neutralist Scandinavian foreign policies.