Purpose: Cantonese lexical tone awareness is closely associated with 1st language Cantonese vocabulary knowledge, but its role in 2nd language English vocabulary knowledge was unclear. We addressed this issue by investigating whether and, if so, how Cantonese lexical tone awareness contributes to English expressive vocabulary knowledge in Hong Kong Cantonese--English bilingual children. Method: A sample of 112 Hong Kong Cantonese--English bilingual 2nd graders were tested on Cantonese lexical tone awareness, English lexical stress sensitivity, Cantonese-- English segmental phonological awareness, and both Cantonese and English expressive vocabulary knowledge. Results: Structural equation modeling analyses revealed that Cantonese lexical tone awareness contributed indirectly to English expressive vocabulary knowledge through English lexical stress sensitivity and Cantonese--English segmental phonological awareness. Conclusion: These results demonstrate the role of Cantonese lexical tone awareness in Cantonese--English bilingual children's English vocabulary knowledge. This also underscores the importance of 1st language suprasegmental phonological awareness in 2nd language expressive vocabulary knowledge.