Private governance raises important questions about democratic representation. Rule making is rarely based on electoral authorisation by those in whose name rules are made—typically a requirement for democratic legitimacy. This requires revisiting the role of representation in input legitimacy in transnational governance, which remains underdeveloped. Focussing on private labour governance, we contrast two approaches to the transnational representation of worker interests in global supply chains: non-governmental organisations providing representative claims versus trade unions providing representative structures. Studying the Bangladesh Accord for Fire and Building Safety, we examine their interaction along three dimensions of democratic representation: 1) creating presence, 2) authorisation, and 3) accountability to affected constituents. We develop a framework that explains when representative claims and structures become complementary but also how the politics of input legitimacy shape whose interests get represented. We conclude by deriving theoretical and normative implications for transnational representation and input legitimacy in global governance.