This article reports on a case study that investigated changes in the motivation of Chinese ESL learners over a three month period of residence in an English-speaking environment. The participants consisted of 11 Chinese ESL learners, who were tertiary students and taking general or academic English courses in New Zealand. They took part in the present research shortly after their arrival in New Zealand. Data were collected over a period of three months using qualitative data collection instruments such as learner diaries and individual interviews. The results revealed some dynamic changes in the motivation of Chinese ESL learners over a three month period of residence in an English-speaking country. According to the similarities and differences in their motivation, they were categorized into five learner types. In general, the learners belonging to the first three types were able to maintain or increase their overall motivation. The learners in the last two types were not able to maintain their overall motivation: Their motivation decreased over the three months.