The increasing diversity in American public schools presents challenges to teachers and administrators. Current methods of reading instruction for English language learners (ELLs) have been ineffective to meet their needs in acquiring vocabulary. Meanwhile, the amount of time afforded ELLs to become proficient with grade-level vocabulary presents challenges for all stakeholders. Consequently, ELL students are not demonstrating growth on Florida's annual standards assessments. The purpose of this qualitative descriptive case study was to explore the vocabulary instruction used by elementary teachers of ELLs in the southeastern United States. The study's contextual framework comprised the five hypotheses of Krashen's second language acquisition theory: acquisition-learning, monitor, natural order, input, and affective filter. The research questions aligned with the theoretical framework and were the means used to identify strategies and describe instruction for ELLs. Nine purposefully selected participants provided rich descriptions of strategies and curricula used during vocabulary instruction to improve language acquisition. Research findings suggest the benefit of promoting partnerships among stakeholders to support vocabulary instruction for ELL students and the importance of continued professional development of vocabulary instruction strategies for staff. An unexpected finding was the value placed on using media for differentiated instruction of academic vocabulary with ELL students. The study provided information for policy and practice on the value of differentiated curriculum with an emphasis on ELLs' language acquisition needs. Future researchers could explore the use of auxiliary resources for ELL students, providing additional opportunities for differentiation in reading vocabulary instruction. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]