The present study examined the relationship between age of acquisition (AoA) and bilingual development for native Chinese children who learned English as a foreign language. A composite test measuring different aspects of language and cognitive skills in Chinese and English was administered on 85 Chinese native primary schoolers, who received bilingual instruction at different points of development (for Chinese, 0 [less than or equal to] AoA [less than or equal to] 7 years; for English, 2 [less than or equal to] AoA [less than or equal to] 10 years). Results found AoA constraints on the outcomes of L1 Chinese acquisition are significantly different from those for L2 English. Not all domains of bilingual skills follow the pattern of "the earlier, the better" in language development. Additionally, L1 AoA made unique contributions to L2 English learning. These findings contribute to our understanding on the nature of the AoA effect on bilingual learning.