There are both educational and cultural benefits to first language (L1) instruction, particularly in the early years of school, but in Australia, few Indigenous language–speaking students are taught in their own languages. Teaching mathematics in Indigenous languages requires both linguistically capable Indigenous educators and the identification and development of suitable mathematics terminology. This paper reports on the collaborative development of a program reintroducing mathematics lessons in Mawng language at Warruwi Community School. This project developed the capacity of an Indigenous educator to take on more responsibility for the content of the class teaching. Lessons focussing on spatifal sequencing terminology were developed to extend students’ use of core Mawng grammatical features while also reinforcing important local cultural knowledge. A collaboration between a non-Indigenous researcher and a Mawng educator, the paper concludes with factors contributing to the sustainability of the project.