Teaching in Sámi schools in the Swedish part of Sápmi where Indigenous Sámi people live should be approached from the perspective of Sámi culture, despite the fact that Sámi culturally based teaching is not specifi cally defined. Therefore, teachers themselves must adapt the teaching and content for Sámi children and, as a result, no Sámi culturally based mathematics teaching usually takes place. The aim of this article is to discuss Sámi teachers’ experiences of Indigenous school transformation and their work to adapt teaching in order to provide Sámi culturally based mathematics lessons. Culturally based mathematics lessons took the form of: Sámi cultural thematic work with ethnomathematical content; multicultural school mathematics with Sámi cultural elements; and Sámi intercultural mathematics teaching. The transformation work took place within an action research study in Sámi Indigenous schools. The teachers changed from a problem- to a possibility- focused cultural teaching perspective and started to act as agents for Indigenous school transformation.