This article focuses on the pedagogical beliefs, practices and ideological assumptions of 15 teachers who work with mother tongue instruction in Sweden. Despite support through provisions in Swedish laws, mother tongue instruction is clearly a marginalized subject, not least due to its non-mandatory status, the limited time allocated for it and the fact that the subject and its teachers are often contested in public debate. In this study, the teachers' narratives center round issues of legitimacy, both for the subject per se and for the teachers' right to be viewed as "real" teachers. In this paper, we highlight how the teachers link mother tongue instruction to the notion of a "common heritage" and how they see themselves as advocates and role models for the mother tongue. The teachers raise the status of mother tongue instruction in a transformational way, to a subject that is essential and can have a positive impact for a group of students who would otherwise be at a disadvantage in the school system. The undermining of mother tongue instruction was found to affect the pedagogical practices, as the teachers often took into consideration how their teaching would be viewed by parents and colleagues.