Academic procrastination is a common behavior among tertiary students. In particular, parttime adult students who undergo professional training usually find it very difficult to balance tertiary study, work, and family responsibilities. It is important to investigate factors contributing to and consequences resulting from adult students’ academic procrastination, so that we can provide them with targeted help. In this study, we collected data from more than 1800 students who participated in a postgraduate training programme for teaching professionals. Specifically, we examined data on assignment grades, student demographic factors, and assignment extensions. Our analysis suggests that students tend to procrastinate on assessment tasks that are not closely related to their professional practice and skills. We also find that students using personal reasons to apply for extensions are more likely to not complete their assignments, even after being given extensions. With regards to demographic factors, female students, students aged 35 and over, and students working at intermediate and composite schools have a higher tendency to postpone their work. By analyzing the grade means and variances of assignments submitted early, on time, and with extensions, we conclude that procrastination is negatively associated with academic performance.