This study uses ethnic capital theory to explore access to secondary mathematics education among linguistically diverse (LD) migrants in metropolitan and regional New South Wales, Australia. Administrative data from over 50,000 students who completed their Higher School Certificate in 2017 were analysed using multilevel logit regressions and marginal effects. The results indicate that, in Greater Sydney, all linguistically diverse first-generation youth took mathematics courses at higher rates than their peers. So did second-generation migrants from Asian backgrounds. Furthermore, considerably larger proportions of students who spoke East Asian, Indo-Aryan, or Arabic languages studied advanced mathematics. Even when only parents spoke these languages at home, their Australian-born children took advanced mathematics more often. Yet, these second-generation students were less overrepresented than those fluent in parental languages. The paper discusses the potential consequences of LD migrant concentration in Greater Sydney, stressing the importance of equitable mathematics education in metropolitan and regional areas.