This study examined dual language learners' (DLLs n = 24) and English-only (EO n = 20) children's expressive and receptive language in kindergarten (M[subscript age] = 5.7 years) as well as the relation to peers' language use. Expressive language skills (vocabulary diversity, syntactic complexity) were measured in the fall, winter, and spring (2014-2015 year). Receptive language skills (vocabulary, sentence comprehension) were measured in the fall and spring. Findings revealed increases in children's expressive and receptive language, except in terms of syntactic complexity. Moreover, peers' vocabulary diversity was positively associated with children's vocabulary diversity. Peers' syntactic complexity was positively associated with children's syntactic complexity and receptive vocabulary. Findings suggest that peers' language use may influence DLLs' and EO children's language learning.