In June 2014, the UN Human Rights Council established an intergovernmental working group to elaborate a treaty on business and human rights. In July 2015, the working group held its first session launching the negotiations process—the culmination of a global movement of non-governmental organizations (NGOs) that over the last four decades have called for greater corporate accountability for human rights violations. The advocacy activities of the Treaty Alliance, an alliance of NGOs that supports the development of the treaty, were pivotal to the tabling of the resolution establishing the working group. These organizations now have the opportunity to engage with the negotiations process, both formally and informally, through consultations, advocacy, and lobbying. This article considers the impact NGOs may have in the drafting negotiations of the proposed treaty. It identifies several lobbying and advocacy strategies that were successful in previous international law-making processes and discusses the extent to which they could be applied to the current negotiations. It presents the benefits of an NGO coalition, of formal and informal lobbying strategies, and of the development of a common NGOs and friendly states framework. It analyses the reasons for Western states’ opposition and suggests lobbying strategies that may overcome it. Recognizing the unique subject matter of this treaty, it also focuses on lobbying corporate actors, and explores the complementarity between the Guiding Principles on Business and Human Rights and the treaty and the need for NGOs to support both. The article concludes on the necessity to compromise on essential points if a treaty is ever to emerge.