<p>Persistent concerns exist internationally regarding teacher shortages and the prevalence of out-of-field teachers in secondary schools. In New Zealand, anecdotal evidence suggests growing difficulty recruiting qualified secondary mathematics teachers, yet little empirical data exist on the scale of the problem, the reliance on out-of-field teachers, or the support they receive. Drawing on communities of practice as a theoretical framework, this study reports findings from a national questionnaire of school leaders and mathematics teachers. We examined the distribution and characteristics of out-of-field teachers, the extent of recruitment difficulty, and how these varied across school contexts. We also explored the challenges they faced and the support available. Findings reveal widespread recruitment difficulties and reliance on out-of-field teachers, with patterns shaped by school size, region, and socio-economic context. Teachers’ experiences highlight the importance of collegial support in enabling progression towards fuller participation in the mathematics teaching community, although variability in support leaves some at the periphery. This study provides the first comprehensive account of out-of-field secondary mathematics teaching in New Zealand, offering insights relevant to international debates on teacher workforce sustainability.</p>