The impact of global activism against trade liberalization is examined in this article through an analysis of the initiatives of cross border civil society networks and with particular attention to the failed 2003 World Trade Organization (WTO) ministerial conference in Cancun. Key aspects considered here include the internal dynamics of mobilization – which was characterized by a strong framing and widespread protest – and the political opportunities in WTO negotiations, which were marked by divisions within the North and resistance by a large group of Southern governments. In the failure of the WTO Millennium Round in Cancun and the loss of momentum of its liberalization agenda, a significant role has been played by civil society activism and its ability to combine protest, well‐prepared lobbying, an epistemic‐like community able to influence public opinion, and the development of alliances with like‐minded governments of the South.