The article contributes to the emerging literature on the intersection of academic mobility and precarity by examining the impact of the 2016 Brexit referendum result on the mobility and immobility projects of migrant academics on temporary contracts. We draw on 22 interviews conducted with early-career researchers in the UK and Switzerland. We examine how the Brexit process threatened participants' sense of citizenship and belonging, heightening their sense of vulnerability both as migrants and as temporary workers, sometimes making immobility the only viable option. We show how it made visible hidden hierarchies and fault lines, prompting unequal strategies as researchers struggled to maintain their prerogatives as members of their communities. Passport privilege and the 'good migrant' figure emerged as central to these individualised strategies. The article challenges the framing of academic mobility as a natural and beneficial career move for early-career researchers grappling with the added uncertainties caused by Brexit.