As the United States continues to grow with English language learners entering schools, teachers must focus on helping them improve their reading comprehension. The problem addressed in this study was the lack of vocabulary instruction implemented by teachers impedes the development of English language learners' reading comprehension. The purpose of this qualitative case study of 10 middle school teachers who teach English language learners in a northern South Carolina school district was to explore their vocabulary instructional methods used to improve their English language learners' reading comprehension. The theoretical frameworks that informed this study were Vygotsky's sociocultural learning and language theories. Data were collected using an online questionnaire and individual interviews, which were audio-recorded through Zoom. The analysis method included coding the participants' responses through the NVivo data analysis software, using six of NVivo's seven-step approach to thematic analysis. Thematic analysis was used to identify patterns and themes within the data gathered from the participants. Findings from the study included that vocabulary instruction was a critical component to how English language learners learn how to apply and use academic vocabulary. The teachers used various teaching methods and tools to develop their students' learning to support their reading and vocabulary development. To help English language learners improve their reading comprehension, it is recommended that teachers use a variety of aids, such as pictures, to help students transfer meaning across contexts. Teachers can also execute small group instruction with English language learners consistently to support and provide constructive feedback about their vocabulary knowledge and reading comprehension. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]