This longitudinal qualitative study explores the motivation and identity development of students in a comprehensive university who are learning English as a second language (L2). It is set in the contemporary People's Republic of China, where dramatic sociocultural, political and economical changes are taking place. Multiple research methods, including interviews, diary studies and recorded interactions, are employed. The author considers in her study both the impact of broader issues such as globalization and more local social development on language learners at tertiary-level in China, and the effects of discourse and community in constructing motivation. This study combines detailed linguistic analysis with sociocultural theory, together with the concept of communities of practice. In so doing, the author investigates the social, historical, linguistic and individualistic factors that combine dynamically over time to co-construct learners' motivation. A critical discourse analysis approach to exploring language learner motivation presents an enhanced understanding of the relationship between motivation and interaction, providing a line of enquiry and manifold new insights.