Research has highlighted that increasing numbers of third‐country migrants who have acquired European Union (EU) citizenship in one EU Member State employ the freedom of movement that it provides to onward migrate to other EU destinations. A range of socio‐economic, cultural, and educational factors have been found to drive migrants to move onward to try to fulfil their migration aspirations across multiple locations. This paper suggests that analysing onward migration through the relational lens proposed by the mobility paradigm better acknowledges the processual and dynamic nature of this migration pattern and its motivations. Drawing from a small‐scale project focusing on Latin American migrants (with EU citizenship) who have relocated from Spain to the UK post‐2008, the paper presents a distinctive form of reactive onward migration. Research is based on secondary data analysis and semi‐structured interviews with key informants from voluntary and statutory organisations in Spain and the UK. It finds that, as their socio‐economic conditions deteriorate in Spain, some Latin Americans decide to mobilise their civic and social capital (EU citizenship, transnational networks) to move to the UK in search of employment. Yet, the full mobilisation of this civic capital is jeopardised by their limited linguistic and economic capital and the structural constraints that these onward migrants encounter in the UK. By considering the factors that mediate some Latin Americans' post‐2008 experiences of stasis and movement between Spain and the UK, this study enhances conceptualisations of onward migration and illuminates cross‐border dynamics of migration and precarity within the EU. Copyright © 2016 John Wiley & Sons, Ltd.