This paper provides a dynamic perspective on the linguistic development of adult bilinguals in an L2 environment, and an empirical test for the principles formulated within a dynamic systems approach to L1 attrition. It presents a qualitative analysis of the personal narratives of the post-migratory linguistic development of 27 adult German–English bilinguals residing in Ireland, with particular focus on two participants’ stories. Participants responded to a comprehensive sociolinguistic questionnaire, providing self-ratings of current and past language proficiency in all their languages, and reflecting on the processes of and factors impacting on L2 acquisition and L1 attrition in the L2 environment. These data are complemented by proficiency data elicited with a test battery in L1 German and L2 English. Analyses revealed that most participants have succeeded both in acquiring English to a high level, and in maintaining German. However, other L2s as a rule show a pattern of decline. The results are discussed with recourse to dynamic conceptions of multilingual development.