Young bilinguals need to learn words in both their languages while navigating two sets of speech sounds. Evidence is mixed as to whether this impacts their encoding of fine phonological detail in words. We used a mispronunciation paradigm to test bilinguals’ and monolinguals’ encoding of phonological detail, using cognate (e.g. banana - banane) and non-cognate words (e.g. apple - pomme) to examine the effect of cross-language phonological overlap. We tested a total of 51 French-English bilingual and English monolingual 24- to 36-month-olds on their recognition of correctly-pronounced and mispronounced familiar words using a looking-while-listening task. In a growth curve analysis, we found that bilinguals showed sensitivity to mispronounced cognate words, but not to mispronounced non-cognate words. This pattern suggests that words with high cross-language phonological overlap have more detailed phonological representations. Our results suggest that bilingual toddlers leverage cross-language phonological overlap to build highly-specified sound representations for cognates earlier than for non-cognates. Studying bilingual learners provides a unique lens for understanding the complex interplay between language experience and phonological representation.