Despite the growth and popularity of Irish-medium Education (IME) in Northern Ireland, the sector has not received the same levels of state support and funding as has heritage language education in the rest of the UK and the Republic of Ireland. Educating children in an immersive language setting, particularly in a minority or endangered language, is still regarded as disadvantageous to the learner, and that bilingual language education will hinder academic attainment, including maths. We present findings from thematic interviews with 11 primary teachers' perceptions on the challenges of teaching maths in Irish, and how to help the sector develop language skills in, and resources for, teaching maths in the primary curriculum in Northern Ireland. The challenges that emerged from the thematic interviews, include finding teachers with the requisite language skills to teach maths, training and support for Irish-speaking maths teachers, and how children can acquire the right kind of fluency to engage in maths learning.