Since the global research into mindfulness meditation (MM) is revealing many positive effects on everyday life for those who practise it, studying its effects on academic performance could be worthwhile. However, the duration of effects of MM on academic performance is still unclear. Thus, this study first investigates the MM influence on short-term and long-term academic performance. The relationship between the meditation depth and short-term academic performance is further explored. The experimental group received the MM intervention while the control group did not. Compared to the control group, the experimental group had better short-term academic performance but similar long-term academic performance. Within the experimental group, students with high meditation depth achieved better short-term academic performance than those with low meditation depth. Finally, the questionnaire results revealed that most students enjoyed the MM process and agreed that the intervention improves in-class learning efficiency.