PURPOSE: In the current study, we examined the alignment of language choice of bilingual parent-child dyads in play-based interactions. METHOD: Forty-four bilingual Spanish-English parent-child dyads participated in a 10-min naturalistic free-play interaction to determine whether bilingual children and their parents respond to each other in the same language(s) across conversational turns and whether children's language ability and children's and parents' language dominance affect language alignment. Children's language ability was indexed by the Bilingual English-Spanish Assessment. Logistic regression was used to test the effects of children's language ability and children's and parents' language dominance on the alignment of language choice. RESULTS: Results revealed that children and parents largely aligned their language choice and that children's and parents' language dominance, but not children's language ability, influenced alignment. Patterns of alignment differed between children and parents. Children aligned to their dominant language, and this was true for both English- and Spanish-dominant children. In contrast, English-dominant parents aligned equally to both languages, whereas Spanish-dominant parents aligned significantly more to Spanish. CONCLUSION: Together, these findings suggest that bilinguals' alignment of language choice is deeply sensitive to language dominance effects in both children and adults but that parents may also choose their language strategically in conversations with their children.