Transnational activism has increased in relation to international trade and development politics in the past decades, yet their power has been inadequately studied. This article analyses the STOP EPAs campaign (2004–2009) which aimed to influence the negotiations of Economic Partnership Agreements between the European Union and African, Caribbean and Pacific countries. It is analysed through a framework in which decisional and discursive power converge. It is argued that the campaign contributed to shaping the negotiations’ discursive practices and, thus, helped to frame what was possible in terms of decisions. It did so by both reproducing and challenging underlying assumptions of trade and development policies, fostering the inclusion of more voices and issues in debates, and shaping subjects’ identities. It was in the ‘play of practice’ that activism opened limited but important spaces for change, as observed in the discussions over what a pro-development World Trade Organization-compatible free trade agreement would entail.