The school-aged population in the United States is becoming more culturally and linguistically diverse, while achievement gaps across content areas persist. At the same time, more rigorous academic demands are being placed on all students, including English language learners (ELLs). Teachers of ELLs face the double challenge of promoting English language and literacy development, as well as academic achievement across subject areas. This article addresses effective professional development to support the teaching of science and English language and literacy to ELLs. First, it highlights what the literature says about teachers' knowledge and practices in teaching science to ELLs. Second, it highlights what the literature says about teacher professional development more broadly, and then specifically in terms of science instruction with ELLs. Finally, it discusses emerging educational policies and their potential implications for professional development of science teachers of ELLs.