Many classrooms include students who use multiple languages other than the school-sanctioned or teacher's language(s). This study asks how English-medium teachers develop language ideologies that support critical translingual literacy instruction. Using a collective case study, we ask how five English-medium teachers in a U.S. graduate course name and act on their language ideologies through literacy instruction. The cross-case analysis indicates the teachers' language ideologies viewed students' L1 use as a source of pride/identity and as a way to promote equity and social justice. These ideologies supported critical translingual literacy instruction through classroom actions (incorporating new texts, initiating family engagement, and positioning students as experts). Implications illustrate the need for literacy teacher education to focus on language ideologies, using literacy instruction as a powerful vehicle to effect language policy. Thus, focusing on critical translingual literacy instruction can support English-medium teachers to act as both literacy and language policymakers.