How are metalinguistic skills associated with vocabulary knowledge in languages with contrasting phonological and morphological properties? To address this question, tasks of phonological awareness and morphological awareness, other reasoning and literacy-related skills, and measures of vocabulary knowledge in Chinese and English, were administered to 217 Hong Kong Chinese kindergarten children learning English as a second language. Syllable-level awareness but not phoneme onset awareness was strongly associated with Chinese vocabulary knowledge; phoneme onset awareness but not syllable awareness was associated with English vocabulary knowledge. In hierarchical regression equations, phonological awareness in English explained unique variance in English vocabulary knowledge but not in Chinese vocabulary knowledge. In contrast, measures of morphological awareness, which were strongly associated with syllable awareness, uniquely explained 13% of the variance in Chinese vocabulary knowledge apart from all other measures included but were not uniquely associated with English vocabulary knowledge. Findings highlight the strong overlap across phonological and morphological awareness in Chinese and the different associations of each to vocabulary acquisition in Chinese (L1) and English (L2) languages.