Bilinguals are more successful than monolinguals in novel language learning due to the transfer of prior learning strategies and experiences with two languages. The extent of such transfer may depend on the similarity between previously acquired languages and a novel language. This hypothesis was tested in relation to vocabulary learning in elementary school children. The sample included 10 Hebrew-Yiddish speakers, 10 Hebrew-English speakers, and 10 monolingual Hebrew speakers who learned ancient Aramaic as part of religious studies. Hebrew-Yiddish speakers, for whom both languages were similar to Aramaic, recalled more Aramaic words than both monolingual speakers and Hebrew-English speakers, for whom only one language was similar to Aramaic. There was no statistically significant difference between Hebrew-English and monolingual speakers. The advantage in the Hebrew-Yiddish group remained significant even after controlling for background variables, such as years of maternal education, phonological short-term memory, and vocabulary size in Hebrew. These findings provide evidence that previously acquired languages may facilitate vocabulary learning in a novel language if they are similar to the novel language.