The chapter describes language socialization research conducted in early childhood education settings with a focus on immigrant children and multilingual peer groups. It outlines the main theoretical concepts: socialization through and to language and culture, conceptualization of socialization as a dynamic, bidirectional process where both adults and young children influence each other’s actions. The chapter describes findings from empirical studies conducted in a variety of sociocultural contexts (European countries, North America, and Asia). They show how children can actively reshape the institutional language ideologies or adhere to these ideologies without showing resistance. The chapter describes major topics, such as children’s agentive participation in using language for socializing processes; monolingual/bilingual language ideologies and language socialization; and teachers’ socializing strategies, their linguistic and cultural implications for language and cultural socialization. Future research directions are discussed in terms of broadening the scope of studies to include a holistic investigation of young children’s multilingual language socialization practices in peer groups, and in families. Concluding, the chapter discusses the importance of children’s peer group and its social norms in shaping the opportunities for second language learning, and the impact of children’s interactions on the establishment of multilingual or monolingual norms, language use and learning, and teachers’ ways to establish rich language and sociocultural ecologies in early education.