English language learners (ELLs) from an urban high school in the southeastern United States struggled to achieve reading proficiency on the federally mandated reading assessments. The purpose of this case study was to gain an understanding of ELL teachers' perceptions about how using effective vocabulary pedagogies affected the reading comprehension of high school ELLs. Guided by Vygotsky's theory of development, the research questions of this study addressed ELL teachers' perceptions of vocabulary instruction and its effect on reading comprehension. The purposeful sampling included 5 high school teachers, an administrator, and an English for students of other languages compliance specialist, who met the criteria of having the experience of providing instruction and/or support to ELLs. These participants were asked during their interviews about their perceptions of vocabulary instruction to improve the reading proficiency of the ELLs, effective vocabulary strategies that affect ELLs' reading comprehension, and the various methods that support and hinder vocabulary instruction to ELLs. Interviews and observations were used to collect data. Data were analyzed using thematic coding to organize the participants' responses through occurring themes and sorted categories. Participants' responded that there should be more professional development about ELL vocabulary instruction and practices. The culminating project may lead to improved instructional vocabulary strategies that will provide an impetus to respond to the learning requirements of all ELLs, resulting in positive change through increased reading success for ELLs in the district at large.