This paper aims to research how left anti-systemic groups in the European Union meet the challenges a transnational political system creates for them. System critical movements have existed for a long time, but in times of an increasingly transnational multi-level polity it is important to consider how system criticism changes. In a qualitative study of six left antisystemic groups from Germany and Sweden, this paper seeks to give insights on left anti-system activism and the role of local groups in connection to transnational social movements. Qualitative interviews with group members, a qualitative content analysis and the connection to Social Movements Theories bring forward a hypothesis of how left anti-systemic groups use political theories, position themselves in the process of political change and what influence they can have on transnational social movements. In order to meet the challenges of (1) the difficulties of defining the political system that the groups are active against (the political system in the EU) (2) more complex and abstract issues that are dealt with (3) the fading importance of the role of the state in the process of political change, the groups adapt by using political literature in an open way and focusing on practical activism. Furthermore, the groups increasingly use transnationalism as a conception for their activism and therefore perceive their main tasks in providing infrastructure and continuous local organization to enable mobilization for transnational social movements. The role suggested for local or national anti-systemic groups in transnational social movements is existential, even though the importance of this role is not always reflected upon by the group members.