The significance of mathematics in the Irish secondary school curriculum is undisputed. However, the persistent challenge of teacher shortages in the subject has garnered substantial attention over the past fifteen years. There has been a change in the numbers entering the mathematics teaching profession, with the number of newly qualified mathematics teachers from the consecutive initial teacher education route particularly affected. A shortage of qualified mathematics teachers has serious implications for effective teaching and student learning outcomes in classrooms. This paper investigates perspectives on the repercussions of ongoing teacher shortages in Irish secondary schools, drawing insights from semi-structured interviews with eight mathematics teachers who graduated from consecutive initial teacher education (ITE) programmes in recent years. We employed thematic analysis and found that their considerations of the main impacts centred around the prevalence of ‘out-of-field’ teachers, larger class sizes, a lack of continuity in teaching, and ensuing gaps in students’ knowledge. Implications for practice are discussed.