This analysis investigates changing mobilization at the ILO in response to the labour and social rights shock created by EU and IMF demands in the EU sovereign debt crisis (Crisis Europe or euro-crisis). Mobilization means the purposeful use of legal norms and institutions by social movements and civil society groups to advance identified policy goals. It can be contrasted with the use of legal norms and institutions by individuals or entities to settle disputes affecting them. After introducing relevant features of euro-crisis and the ILO, the article develops an analysis that measures changing mobilization at the ILO during euro-crisis. It then shows how such an analysis makes two key contributions: first, to our understanding of the ILO and, second, to how we approach mobilization. First, by viewing the ILO as a rights mobilization structure, it shows the vitality and interest of doubted or neglected ILO supervision and complaints mechanisms. Five elements are underlined: the ILO is more than existing literature assumes; it questions the depiction of the ILO as a ‘toothless tiger’; the sharp divide between unions and NGOs is overstated; certain institutional design features make the ILO a good venue for transnational mobilization; the ILO is not transparent in terms of access to documents relevant to mobilization and compares poorly in this respect with UN Human Rights Treaty Bodies. Second, by setting it against existing literature, it is shown how measuring mobilization is distinctive within the broader human rights mobilization scholarship. The most important insights it introduces are: rejecting the assumption that mobilization inevitably follows a significant rights shock such as euro-crisis; addressing the puzzles of union ‘mobilization’ and motivation; operationalizing measurement of mobilization against the backdrop of venue choices; considering how to deal with an international organization which is both a mobilization venue and an engaged actor.