Methodological nationalism is a cognitive bias that construes states as the natural and necessary form of contemporary social organisation. This gives rise to a state-centred view which naturalises national communities, exaggerates the differences between citizens and migrants, and exceptionalises international migration. In this paper, I argue that methodological nationalism is not only empirically inaccurate, but also normatively problematic, because its assumptions prevent migration ethicists from properly theorising about discrimination. I begin by briefly presenting methodological nationalism and clarifying some misconceptions. I (...) also identify some features that would make a policy discriminatory and show that many contemporary migration policies are discriminatory. Looking at three variants of methodological nationalism (naturalisation, territorialisation, and ignorance), I argue that methodological nationalism marginalises concerns about discrimination in migration ethics and prevents migration ethicists from developing accounts that would be able to counter xenophobic arguments. Last, I consider the implications of my argument for migration ethics. (shrink)