Dual Language Learners (DLLs) are children whose first language is a language other than English or children who are developing two or more languages, one of which may be English. To tailor services effectively for these students, California State Preschool Programs (CSPPs) are required to follow a two-step process for DLL identification. This guide is dedicated to ensuring DLL identification is a positive experience for providers, emphasizing the important role it plays in building strong relationships with DLL children and their families. It covers essential DLL identification principles, effective family engagement strategies, objectives of the Family Language Instrument and Family Language and Interest Interview, and valuable insights into using data for DLL services.