This article draws on a range of case studies to explain how worker posting can cause hierarchised labour mobility, involving nationality-based hierarchies in pay and conditions between workers in the same labour markets or work sites. This hierarchisation is most apparent on large construction sites, where companies systematically use posting for labour cost advantage, but it is also found on smaller sites and in other sectors besides construction. The article outlines three features of this low-wage posting system—worker hypermobility and dependency, transnational enforcement challenges, and multifaceted employer arbitrage strategies—that conspire to maintain posting as a form of hierarchised mobility. We argue that posting undermines many countervailing forces that typically mediate hierarchisation.