Learners who begin to acquire a second language (L2) in a naturalistic environment after puberty are thought to be constrained by biological age factors and to have greater difficulty obtaining native-like L2. However, the extant literature suggests that L2 acquisition may be positively affected by post-maturational factors, such as acculturation. This exploratory study examined the relationship between acculturation and L2 acquisition on Chinese-English late learners. Chinese students who arrived in the USA after puberty were examined to see whether the acculturation process towards US society was associated with higher speaking proficiency levels and more native-like pronunciation of English language. The results suggest that acculturation relates to speaking proficiency but not pronunciation.