As the population of young children from culturally and linguistically diverse (CLD) backgrounds grows in the U.S., so too does awareness of the need for interventions to promote their language development and reduce the “word gap.” This synthesis described and analyzed studies examining interventions for improving language outcomes for young, CLD children (birth through age 5). The purpose was to discuss how cultural and linguistic factors were addressed in the interventions, examine the methodological rigor of the studies, identify the outcomes and measures used, determine the efficacy of the interventions on language skills in English and in children’s home language(s), and describe the reported social validity of the interventions. Forty articles reporting on 41 studies met inclusionary criteria. Interventions focused on four areas: explicit instruction on targeted skills; classroom curriculum interventions; interactive book reading and/or book making interventions; and naturalistic, routines-based interventions. Most interventions were delivered to children above age 3 who were from Latino and/or Spanish-speaking backgrounds. Also, linguistic adaptations (primarily in Spanish) were more common in interventions as compared to cultural adaptations. Vocabulary was the most common outcome targeted, with a wide variety of measures used across studies. Most interventions had positive effects in English and/or a language other than English particularly when the interventions were linguistically- and culturally-responsive. Several cultural or linguistic factors were also identified as variables affecting intervention fidelity, engagement, and effects. Limitations of the current research base and implications for practice are discussed. (author abstract)