This paper aims to engage with and respond to recent calls in the literature for a unifying theoretical framework to understand second language teacher education (SLTE). It critically reviews the major conceptualizations of SLTE in relation to the key conceptualizations of second language (L2) teaching. The review identifies shortcomings in traditional perspectives on L2 teaching and SLTE and the need to re-conceptualize SLTE as a field. A recent re-conceptualization of SLTE is seen through the shift towards a social constructivist perspective, a redefinition of the knowledge base, research that responds to the epistemological shift, and a sociocultural perspective on SLTE. The existing literature shows that although there is now a growing body of research that looks into the various dimensions of SLTE, few studies have gained a comprehensive and systematic view of the complexities of SLTE. The paper argues that a sociocultural perspective, especially a combination of Vygotsky’s genetic method and Engeström’s proposal of the third generation of activity theory, has become a powerful way of understanding L2 teacher learning, which corresponds to the need for a re-conceptualization of SLTE. This paper calls for more research using a sociocultural framework to enrich its knowledge base.