The purpose of this study was to explore the use of code-switching in the narratives of dual-language Latino preschoolers, specifically by examining its incidence, types, functions, and grammaticality. Previous work has investigated code-switching in younger children and in older children and adults, but relatively little work has investigated code-switching during the preschool years, an important time for dual-language development. This study tracked the code-switching of 39 Latino DLL preschoolers over three time points: the end of each of their two preschool years, and the beginning of their kindergarten year. At each time point, children shared a wordless picture book narrative. Code-switching in their narratives was coded for incidence, type, function, and grammaticality. Results showed that the number of children who code-switched was relatively small and stable over time, and that most code-switches occurred from Spanish to English. One-word switches, mostly nouns, were the predominant type of code-switching across years. Children used code-switching to serve a variety of functions, and almost all switches adhered to grammatical rules. Results suggest that the preschool age is an important developmental period for code-switching, in which children's code-switches are simultaneously reflective of those of younger children and associated with more complexity in function and grammaticality.