Purpose: This study examined the role of the language of vocabulary instruction in promoting English vocabulary in preschool Latino dual language learners (DLLs). The authors compared the effectiveness of delivering a single evidence-informed vocabulary approach using English as the language of vocabulary instruction (English culturally responsive [ECR]) versus using a bilingual modality that strategically combined Spanish and English (culturally and linguistically responsive [CLR]). Method: Forty-two DLL Spanish-speaking preschoolers were randomly assigned to the ECR group (n = 22) or CLR group (n = 20). Thirty English words were presented during small-group shared readings in their preschools 3 times a week for 5 weeks. Multilevel models were used to examine group differences in postinstruction scores on 2 Spanish and 2 English vocabulary assessments at instruction end and follow-up. Results: Children receiving instruction in the CLR bilingual modality had significantly higher posttest scores (than those receiving the ECR English-only instruction) on Spanish and English vocabulary assessments at instruction end and on the Spanish vocabulary assessment at follow-up, even after controlling for preinstruction scores. Conclusions: The results provide additional evidence of the benefits of strategically combining the first and second language to promote English and Spanish vocabulary development in this population. Future directions for research and clinical applications are discussed.