Scholars have intensely debated the conditions under which trade unions can successfully mobilize professionals. We explore an internationally comparative perspective on mobilizing professionals by asking how two nurse unions in the United States and Germany successfully limited management's prerogative over staffing levels. We found that German national institutions had little influence over the bargaining process; instead, factors at the level of organizations and their environment (leadership support, organizational restructuring, coalitionbuilding with supportive stakeholders and framing) enabled mobilization. Based on a power resources perspective, we conclude that unions can mobilize professionals using militancy, even without much support from national institutions.In response to declining densities, trade unions in the Global North have adopted militant tactics such as protests, one-to-one organizing and strikes. In the United States, the United Kingdom and Australia, trade union confederations have since the 1980s created training institutions to promote organizing (Heery 2002). Since the early 2000s, German unions have also adopted organizing in Germany's coordinated, macro-institutional context (Greer 2008;Nachtwey and Wolf 2013). Moreover, Change to Win's European Organising Centre has greatly supported new strategies across Europe, including organizing in hospitals (Givan and Eaton Forthcoming).At the same time, national average densities have continued to decline (Ibsen and Tapia 2017). In the meantime, professionalization processes such as licensing have increased, perhaps indicating that such professionalization