Vocabulary learning is central to reading ability and academic achievement. Vocabulary researchers and educators have viewed its essence as a process of associating the pronunciations and meanings of words in memory, and they have paid little attention to the contribution that spellings might make to vocabulary learning. We review theory and evidence showing that this is a serious oversight. Once children become literate, they retain the spellings of words bonded to their pronunciations and meanings in memory. Several studies show that spellings of words are retained in memory and influence phonemic and syllabic segmentation of words, they enhance memory for pseudowords, and they impact the detection of oral rhyming words. Two studies show that exposing second and fifth graders to the spellings of new vocabulary words enhances their memory for pronunciations and meanings of the words. Students with better developed orthographic knowledge benefit more from spellings in learning vocabulary words than students with weaker knowledge. In fact, the detection of a Matthew effect suggests that differences in orthographic knowledge create a difference in vocabulary size that grows increasingly large over time. Findings carry implications for enhancing vocabulary learning and instruction. Teachers need to show the spellings of new vocabulary words when they discuss their meanings. Students need to stop and pronounce unfamiliar words rather than skip them during independent reading. Researchers need to incorporate orthography into their theories explaining vocabulary acquisition, specifically phonological working memory theories, and they need to attend to its influence in studies they conduct.