Mother tongue-based education (MTBE), involving the use of learners' first or predominant community language as a medium of instruction, has important implications for health literacy and health promotion beyond the classroom. This position paper examines its potential to strengthen health promotion in schools and communities in Nigeria and the wider West African context. Drawing on literature on multilingual education, language policy, health communication, and school health, the paper argues that MTBE can improve comprehension of health information, cultural relevance, community engagement, and the adoption of appropriate health practices. However, its effective implementation is constrained by linguistic diversity, inadequate indigenous-language health terminology and instructional materials, limited teacher and health educator preparation, weak policy implementation, and societal preference for dominant international languages. The paper proposes strengthening indigenous-language health resources, capacity building, community participation, multilingual digital technologies, and effective implementation of language policies. MTBE can therefore support more inclusive, culturally responsive, and equitable health promotion.