PurposeThe incidence of subthreshold depression (StD) in adolescents is growing rapidly, which in turn is known to impair functioning and increase the risk of major depression. It is therefore important to provide effective intervention to prevent the transition from StD to major depression. As a traditional Chinese mind-body exercise, Tai Chi Chuan (TCC) may be an available selection. Researchers have shown the effectiveness of mindfulness-based therapy on depression; however, for the StD youth, there have been no studies to investigate whether mindfulness-based Tai Chi Chuan (MTCC) can be recommended as an effective exercise for improving their psychological state. The aim of present study was to evaluate the effect of MTCC on psychological outcomes of StD adolescents including the depression levels and mindfulness state in a randomized controlled trial (RCT).Patients and methodsAn RCT was carried out. A sample of 64 participants who meet the inclusion criteria agreed to be arranged randomly to either the MTCC group (n=32) or the control group (n=32). Participants of the MTCC group received an 8-week, 2 days per week, 90-minute MTCC intervention for each session. Usual physical curriculum was administered to the participants in the control group. The effectiveness of MTCC training was measured by blinded evaluators through validated scales, which included depressive symptoms, stress, and mindfulness level before and after the intervention.ResultsSignificant improvements in psychological health were observed from MTCC groups. After 8-week intervention, superior outcomes were also observed for MTCC when compared with control group for decrease in depression (F=59.482, P<0.001) and stress level (F=59.482, P<0.001) and increase in mindfulness (F=59.482, P<0.001).ConclusionThe findings of this preliminary study indicated the effects of the MTCC intervention on depression level among StD youngsters. This study provides preliminary evidence that MTCC is suitable for Chinese adolescents and is effective in decreasing depression level.