Although the concept of agency has received a lot of interest in recent educational research, its significance in language learning biographies as well as contextual and relational aspects of learner agency are still little studied. This paper aims at a more thorough understanding of agency by studying student teachers' previous language learning experiences. This paper is based on a dialogical analysis of 12 student teachers' biographical essays describing their relationship with English as a foreign language. The participants are students in a Finnish class teacher and language teacher education programme that uses English as the primary medium of instruction. The study proposes a tripartite model to better understand different dimensions of life-course agency and its implications for language teacher education. The study has its origins in an ongoing action research project aiming at developing dialogic pedagogical practices for language and teacher education at the University of Jyväskylä, Finland.