Few studies on the role of bilingualism in mathematics classrooms explore the intersection of biliteracy, language use, mathematical discourse, and numeracy-especially at the middle school level. Drawing from biliteracy development theory and reform mathematics education literature, this qualitative case study of a dual-language mathematics classroom shows how English language learners (ELLs)/bilinguals use their first (L1) and second language (L2) as resources to access advanced mathematical curriculum. The article provides glimpses of instructional strategies that encourage mathematics discourse and biliteracy development. Encouraging secondary bilingual students to solve non-routine mathematical problems collaboratively may not only promote student engagement but also promote binumerate development.