The purpose of this literature review is to identify the most effective instructional principles for English language learners (ELLs) as documented by prominent researchers in the field and existing research reviews. This report is intended as a high-level synthesis of existing reviews of the literature rather than a comprehensive search and documentation of all primary research articles on ELL teaching and learning. To this end, this review lists the most effective principles for ELL instruction and documents the supporting research evidence for those principles. Principles 1 and 2 are about implementing challenging curriculum and designing the academic content. Principles 3, 4, and 5 are about effective instruction and the available strategies teachers may use in their teaching. Principles 6 and 7 deal with how to teach ELLs to acquire vocabulary and build reading ability. Principle 8 focuses on how to teach ELLs to use the English language. Last, Principle 9 is about the integration of four language skills: reading, writing, speaking, and listening.