Case is one of the most heterogeneous nominal morphological categories: the number of case forms in morphological paradigms, the syntactic and semantic functions of case, and the set of declension classes differ even in typologically similar languages. Hence, the acquisition of case presents the child with a major learning challenge. This article presents empirical studies and theoretical perspectives on case acquisition in children, focusing on generative, natural morphology, cognitive-functional, and usage-based approaches. The empirical focus is on the acquisition of accusative, ergative, and split case systems. The article also explores productivity in children's early case forms, the role of nature or nurture in the acquisition of case, form-meaning mappings in the acquisition of case, and the time course of case development.