The number of Chinese students who are joining international exchange programs has increased significantly in recent years, with the majority enrolling in English-medium courses in the host country. To better understand how to prepare and support their learning, the present study investigated the developmental trajectories of 149 students from a Hong Kong university who participated in a semester-long exchange program in an English-speaking country. By way of questionnaire surveys, in-depth interviews, and document analysis (e.g., study plans, responses to email prompts), this mixed methods inquiry tracked their evolving attitudes, motivation, and depth of investment in language and intercultural learning. As well as individual differences, the findings brought to light environmental factors that led to differing outcomes. While some participants developed more self-efficacy in English and meaningful intercultural friendships, others found it difficult to overcome language and cultural barriers, suggesting the need for interventions to bolster language enhancement and intercultural engagement.