Studies on multilingual word learning have focused on identifying a bilingual advantage over monolingual peers, paying little attention to the relationships between bilinguals' existing vocabulary size and novel word learning. This study compared monolingual and bilingual school-age children on word learning tasks in familiar and unfamiliar languages and examined the relationships between bilingual vocabulary and multilingual word learning. The results showed no significant differences between monolingual and bilingual children in any of the word learning tasks. In addition, the results suggested that bilingual children use vocabulary in the languages they know in a specific way; whereas vocabulary in the dominant language seems to have a facilitative role for word learning in any language (language-dominant pattern), vocabulary in the non-dominant language is used only when learning new words in that particular language (language-dependent pattern).