This paper is situated at the confluence of two emerging areas of research: a lifecourse approach in internal migration studies and in geography more broadly and studies of sub-populations within lifecourse research. The paper aims to better understand the complexities of ethnic group migration in Britain, in particular why young adults of some ethnic groups are more residentially mobile than others. The paper draws on theories of norms of transition to adulthood. UK Census microdata of migration within Britain by age and ethnic group are used. The paper shows ethnic similarities: internal migration patterns that are distinct in young adulthood compared with other ages and many common characteristics of residential mobility. However, there are also differences between ethnic groups in levels of internal migration and in how young adult life events are associated with migration. In particular, partnership brings increased residential mobility for White British young adults but reduced mobility for South Asian young adults with females in both cases being the 'partnership movers'. Being a student increases residential mobility for White British and Chinese young adults but reduces mobility for young adults from Black and South Asian ethnic groups (particularly for females in the Pakistani ethnic group). This raises issues of access to higher education. The paper concludes that a lifecourse perspective provides an understanding of ethnic differences in internal migration that were previously lacking from 'segregation' perspectives. © 2011 The Author. Transactions of the Institute of British Geographers © 2011 Royal Geographical Society (with the Institute of British Geographers).