According to the Oxford English Dictionary (OED), experience is the knowledge or mastery of an event or subject gained through involvement in or exposure to it. Provided that other conditions are invariant, it is believed that a student with more experience in thesis writing tends to do better than others. For most postgraduate students, writing a thesis in a second language is a big challenge. The author believes that former students’ experience of thesis writing in a second language can inform incoming postgraduate students and aspects of postgraduate education. As only very few studies had been done on such experience, the current study was designed to explore postgraduate students’ experience of thesis writing in a second language held by three postgraduate students in one university in Macao. The current study adopted case study as the main research method. Three postgraduate students were selected respectively from three different faculties as the research participants. The research data was gathered by interviewing the three participants individually and analyzed by a phenomenographic method. In addition, in the current study, each participant was interviewed twice, with the first round of interviews being conducted while the participants were writing their theses and the second round after the finalization of the theses. It was hoped that such an arrangement would make possible a more complete depiction of the participant’s thesis-writing experience. . iv The research found that during the process of writing thesis in a second language, the writing experience could be classified into three categories. The first category was challenges, including challenges from searching and reading English literature, L2 writing anxiety and language issues. The second category was ways to deal with those challenges, including more reading, more practicing and seeking help. The last category was called other writing experience in which more practical L2 writing experience was shared. Under each category, there were some subcategories and the experience was described in more detail. In addition, at the end of the current study, the limitations were mentioned and further research about the experience of thesis writing in a second language was also suggested.