Though Mandarin Chinese dual language immersion (DLI) has been growing rapidly in the U.S., research on this population is still rare. This study explored cross-language transfer of expressive oral vocabulary knowledge and definition skills among students in a Chinese DLI program. We found significant within and cross-language relationships of aspects of definition skills and cross-language relationships between expressive vocabulary and definition skills. Hierarchical regression revealed strong predictive association within and across languages for definition skills. Moderation analysis revealed that Chinese vocabulary knowledge had a moderating effect on the transfer of the syntagmatic aspect of Chinese definition skill to the corresponding skill in English. Educational implications and research recommendations are discussed in relation to an expanding framework of cross-language transfer.