Learning new words is a crucial skill across the lifespan, with vocabulary knowledge having wide-reaching implications for education, communication, and wellbeing. The Complementary Learning Systems model provides a useful framework for decomposing word learning into encoding and consolidation processes (Davis & Gaskell, 2009). We previously proposed that existing vocabulary knowledge plays a supporting role in consolidating new words, providing a neurocognitive account for the increasing word gap across development (James et al., 2017). In this talk, I will revisit three of the key proposals in light of recent evidence. First, I will discuss ways in which knowledge of related words can support new word memory in place of offline consolidation mechanisms. Second, I will review evidence suggesting that adults rely on prior knowledge to a greater extent than children, whereas children experience larger memory gains offline. Third, I will reconsider the role that individual differences in existing vocabulary knowledge might play in supporting consolidation, considering its more robust relationship with initial learning. I will end by recommending the next steps for determining the role of prior knowledge in vocabulary learning, highlighting its importance for understanding how learning mechanisms change across development.