["JCMS: Journal of Common Market Studies, Volume 64, Issue 4, Page 1431-1452, July 2026. ", "\nAbstract\nThe EU–Mercosur Association Agreement negotiations have become a focal point for examining the limits of civil society engagement in EU trade policy‐making. This article analyses the design, implementation and outcomes of participatory mechanisms – including Civil Society Dialogues, Domestic Advisory Groups and the European Economic and Social Committee – through the lens of the Modes of Participation framework. Combining a systematic analysis of 230 policy documents with semi‐structured interviews with 14 civil society representatives, the study reveals how these mechanisms often prioritise procedural legitimacy whilst marginalising non‐business actors and limiting substantive influence. Particular attention is paid to informal governance practices and the role of ‘created spaces’ that emerge in response to institutional shortcomings. The findings challenge functionalist assumptions about the legitimising power of participation and emphasise how participatory structures can serve to manage dissent and reproduce power asymmetries. The study contributes to debates on legitimacy, transparency and politicisation in EU trade policy, underscoring the need for more inclusive and accountable forms of governance.\n"]