In bilingual language environments, children learn twolanguages in the same amount of time that monolingualchildren learn one, and children do not learn their twolanguages at exactly the same rate. Furthermore, learning twolanguages requires children to deal with challenges not foundin monolingual input, notably the use of two languages withinone utterance (Do you like the perro?/¿Te gusta el doggy?).For bilinguals of all ages, switching between languages canimpede processing efficiency. But are all switches equallychallenging? We tested Spanish-English bilingual toddlers’processing of single-language and mixed-language sentencesin both languages. We found asymmetrical switch costs whentoddlers were tested in their dominant vs. non-dominantlanguage, and toddlers benefited from hearing nounsproduced in their dominant language. These results suggest animportant commonality between monolingualism andbilingualism: when toddlers have more robust representationsof a particular item, they can better recognize it in diversecontexts.