This chapter explains the neurobiological foundations of first language acquisition in children and relates them to the evolution of language. The neurocognitive characteristics of the multilingual brain are also presented. The general development of cognition, which runs parallel to the child’s language acquisition, forms the basis for the child’s linguistic communication. Prenatal and early childhood brain development is used to show how the child’s brain can continuously carry out more complex cognitive and linguistic processes. The maturation of the child’s brain enables the development of a mental lexicon and the application of morphosyntactic rules parallel to the development of general cognitive abilities. Against the background of brain development and functional neuroanatomy, psycholinguistic findings on the course of language acquisition are presented. Finally, questions about the neurobiological foundations of multilingualism are discussed.