Understanding the value of monocultural acculturation orientation to the host culture (assimilation) and bicultural acculturation orientation (integration) for language learning is critical in guiding educational policy and practices for immigrant students. This study aimed to enhance our understanding on the relationship between acculturation orientation and second language (L2) learning. It generated two conceptual models to describe how cultural identification affects language learning as hypothesized in different theories on identity and L2 learning and tested these two hypothesized models in the immigration context of Hong Kong. A survey was conducted among a group of senior high school South Asian minority students on their learning of the language of the host culture, Chinese, to provide the basis for comparison. It was found that the students mainly adopted the bicultural/integration orientation and that bicultural orientation was the optimal acculturation orientation for learning Chinese. Bicultural orientation influenced the participants' Chinese language learning outcome through impacting psychosocial well-being and engagement with the target language and community. The findings suggest that we need to take both linguistic and psychosocial adjustment factors into consideration when conceptualizing the role of identity in L2 learning. Furthermore, this study cautions us against a context-independent stance toward the utility of assimilation for language learning.