Robust vocabulary instruction is an important part of comprehensive English language arts (ELA) instruction. Vocabulary instruction supports students in learning the meaning of words to build a receptive vocabulary that they can rely on to comprehend the words they read and hear. Many students with significant cognitive disabilities (SCD) and complex communication needs (CCN) struggle to read or understand grade-level words, concepts, and texts. Explicit vocabulary instruction can play an important role in addressing this area of need. Addressing the vocabulary needs of students with SCD and CCN in a comprehensive way calls for a greater investment of instructional time to build their receptive vocabulary and conceptual understandings of new vocabulary. It calls for leveraging the high frequency expressive vocabulary students are likely to have available on their augmentative and alternative communication (AAC) systems to make meaningful connections and demonstrate their understanding of new vocabulary. The aim is successful comprehension across ELA and other academic domains through a robust and expanding receptive vocabulary that extends beyond the words commonly programmed onto AAC systems. Finally, vocabulary instruction should be one part of a comprehensive approach to ELA instruction, with substantial time and effort also devoted to reading and writing instruction so that one day students with SCD and CCN can use spelling and writing to bridge the gap between the words they know and the words they have access to use expressively.