This article draws on a longitudinal study of a group of mainland Chinese students' English learning experiences in an English medium university in Hong Kong, and explores the dynamic nature of their language learning motivation prior to and after their arrival in Hong Kong. The study identified "context-mediated" and "self-determined" elements in the participants' learning motivational discourses. The "context-mediated" motivational discourses echoed the societal discourses of learning, and were shaped by the contextual conditions on the Chinese mainland and in Hong Kong, including the roles of English, academic competition and medium of instruction. Through an extended socialization process, mediated by various social agents, some of these "context-mediated" motivational discourses became internalized and transformed into "self-determined" ones among many participants in later stages of their learning. The article argues for an integrated perspective, viewing learner motivation as a dynamic construct emerging from learners' interaction with contextual conditions. (Contains 1 table and 1 figure.)