This article uses the “communicative repertoire” conceptual framework to investigate the evolving linguistic practices in the Sri Lankan Tamil (SLT) diaspora, looking specifically at how changing mobility patterns have had an influence on heritage language use. Drawing on fieldwork undertaken with 42 participants of diverse migration trajectories in London, the study finds that onward migration has important implications for Tamil language maintenance and use in the UK, and for the introduction of European languages into the community. It argues that Tamil practices can only be fully understood if we consider them within the context of participants' communicative repertoires. Further, the definition of Tamil needs to be expanded to include different varieties, registers and styles that have been shaped by onward migration. As the trend of multiple migrations is becoming increasingly common in globalization processes, studying the recent change in SLT migratory patterns is also crucial to gaining insight into the diversities and transnational links that exist within and across diaspora communities respectively.