Previous research has documented the beneficial effect of Tai Chi, but most of the studies focused on elders and patients with specific health conditions. The aim of the study was to test whether Tai Chi can help to improve self-concept in adolescents with a longitudinal study. The sample comprised 160 students from a Chinese middle school; half of students formed the experimental group and the rest formed the control group. A 1-year Tai Chi intervention was delivered in 60-minute sessions, five times a week. Both groups were instructed to complete the measure of self-concept at the beginning and end of the intervention. Statistical analysis shows the significant reduction of good behaviour, intellectual and school status, popularity and anxiety in the experimental group compared with the control group. The results suggest that the Tai Chi intervention could improve self-concept in adolescents.