Given the potential for phonotactic patterns to affect lexical acquisition through the processes of word segmentation and constraining potential word forms, early knowledge of phonotactic patterns may be connected to vocabulary size. There may be a complex relation between the two. First, infants who do not show strong native language-specific processing may be at a disadvantage in vocabulary development. Furthermore, the influence is likely to be bidirectional; extracting phonotactic information from the ambient language may facilitate vocabulary acquisition, and accumulating vocabulary knowledge may facilitate the discovery of phonotactic patterns and broadly strengthen phonological representations. In the current research, we took an essential step toward understanding these proposed relations by investigating whether an association between phonotactic knowledge and vocabulary knowledge exists during infancy.