This article investigates the patterns of language use among a selected group of trilingual Chinese immigrant children. The study is located in a socio-cultural-linguistic context of a Chinese heritage language school in Montreal, Quebec. Drawing on data collected from classroom observations, I explore how children’s language choices are influenced by their socialization networks, friendship patterns and daily social interactions. The analysis of data is guided by sociocultural theory and the theory of language socialization. The findings indicate that socialization and political institutional contexts can have powerful influences on children’s social and educational development, including language development, identity formation, and mother tongue maintenance and loss.