This article describes the importance of vocabulary knowledge in adolescents' reading comprehension, particularly for students with disabilities. Students with stronger vocabularies tend to have better background knowledge and improved understanding of content-area texts. We describe evidence-based vocabulary instructional practices that practitioners can implement to improve students' vocabulary knowledge and reading comprehension. Effective vocabulary instruction includes (a) teacher-directed, explicit instruction using student-friendly word meanings, (b) text-based instruction that includes classroom discourse focused on the new words, and (c) morphology-based vocabulary instruction. We provide an example of explicit vocabulary instruction that includes before-reading, during-reading, and after-reading routines. [This paper was published in "TEACHING Exceptional Children" (EJ1163963).]