Why do transnational actors choose to campaign on specific issues, and why do they launch campaigns when they do? In this article, we theorize the membership, focus, timing and strategies used in transnational advocacy campaigns as a function of long-standing professional networks between NGOs and individual professional campaigners. Unlike previous scholarship that highlights the role of powerful ‘gatekeeper’ organizations whose central position within transnational issue-networks allows them to promote or block specific issues, we draw on recent work in organizational sociology to bring into focus a wider transnational community of individuals and organizations whose competition for professional growth and ‘issue-control’ is crucial in defining the transnational advocacy agenda. In doing so, we qualify existing notions of agenda-setting and gatekeeping in International Relations (IR) scholarship. To illustrate our theory we use a longitudinal network analysis approach, alongside extensive interviews and analysis of primary non-governmental organization (NGO) sources. Our empirical focus is on transnational disarmament advocacy. However, our theoretical analysis has implications for transnational advocacy more broadly.