This research project was carried out at a police university in southern Vietnam. The objective was to uncover the factors that demotivate the cadets studying at the university in learning English for Special Purposes (ESP). The variables were divided into four groups: (1) teacher-related, (2) cadet-related, (3) infrastructure-related, and (4) university/faculty-related. In this study, a combination of quantitative and qualitative research methods has been used to process data collected from questionnaires sent to 155 second-year cadets, and interviews conducted with 30 cadets. The findings of the study show that there are no demotivating factors coming from the teachers. In fact, what causes the loss of motivation are the cadets themselves, the infrastructure, and the university/faculty. The findings also help in suggesting how to improve the cadets’ ESP learning at the police university in particular and at other institutions in general.