This article illustrates how Mapuche Indigenous knowledge (Kimun) and language (Mapudungun) incorporated into an Intercultural Bilingual Education (IBE) program of a school within a Mapuche context in Chile creates decolonizing counter-hegemonic narratives as forms of culturally relevant pedagogy. Based on a six-month school ethnography, this study focuses on the role of an ancestral educator (Kimche) who, as a teacher in the IBE program, becomes an agent of Indigenous cultural and linguistic transmission as he brings Indigenous knowledge into the classroom as his main curricular objectives. Framed within the complex historical, socio-cultural and political contexts of Indigenous education in Latin America and in Chile, this article highlights the current debates about IBE inside and outside Indigenous communities, which are defining the sustainability of these programs.