This article seeks to provide a theoretical overview of bilingualism and discuss the key concepts and theories that inform classroom pedagogy with bilingual learners. Although some specific classroom strategies are introduced, the primary purpose is not to offer strategies, but rather to offer guiding principles based on theory and research to inform selection of strategies for working with bilingual learners. The first section explores the nature of bilingualism and its development and common myths and beliefs. The second section identifies key issues and concepts in bilingual education and explores an additive approach to bilingual learners, outlining broad pedagogical principles to inform classroom practices across years K-12.