We tested children attending bilingual Hebrew–Arabic kindergartens on a fast mapping task. These early sequential bilinguals included those with Hebrew as their home language and those with Arabic as their home language. They were compared to monolingual Hebrew and Arabic speakers. The children saw pictures of unfamiliar objects and were taught pseudowords as the object names that followed typical Hebrew, typical Arabic, or neutral phonotactics. Memory, phonological, and morphological abilities were also measured. The bilingual groups performed similarly to each other, and better than the monolingual groups, who also performed similarly to each other. Memory and the interaction between language experience and metalinguistic abilities (phonological and morphological awareness) significantly accounted for variance on the fast mapping tasks. We predicted that bilinguals would be more sensitive to phonotactics than monolinguals. Instead, we found that Arabic speakers (bilinguals and monolinguals) performed better with Hebrew-like stimuli than with Arabic-like stimuli, and no effect of phonotactics for Hebrew speakers. This may reflect the diglossia in Arabic language acquisition. The results suggest that the process of fast mapping is sharpened by multilingual experience, and may be sensitive to sociolinguistic factors such as diglossia.