In a two-year longitudinal study we examined if and how syntactic awareness in L1 Chinese influenced reading comprehension in L2 English, a typologically different script. Participants were 401 Chinese-English bilingual children from Hong Kong. We assessed their word order, morphosyntactic, and reading comprehension skills in L1 Chinese and L2 English, and retested them after one year. Results showed that L1 syntactic awareness cross-linguistically predicted L2 reading comprehension over time; this prospective relationship was mediated by L2 syntactic awareness but not L1 reading comprehension. Moreover, similarity in syntactic structure was important in determining the degree of transfer. The comparable word-order structure between L1 and L2, thus less syntactic distance, rendered word order awareness more transferable than morphosyntactic awareness. Our findings suggest that teachers may evoke L1 syntactic features and map them onto L2 corresponding structures to facilitate reading comprehension in L2. Copyright © 2020 The Authors. Published by Elsevier Ltd.