The environmental, economic, social and cultural effects brought on by Genetically Modified Seeds-GMS and their control by transnational corporations like Monsanto has encouraged social collective action, lead by NGOs, both internationally and in Colombia. The main objective is to analyze how the NGO “Semillas” has managed to influence Colombian policies regarding the introduction and use of GMS during the period 2002-2013. It focuses on the Theory of Transnational Advocacy Networks by M. Keck and K. Sikkink (1998). Moreover, the role of environmental NGOs and transnational corporations will be analyzed. The central argument is that by creating links with national and international actors and by creating networks and campaigns with transnational impact, “Semillas” has positioned the debate against SGM and has managed to partially pressure the State by influencing its policies and laws, as well as its speech facing the use of SGM.