Context: Tai Chi is a physical activity modality which is widely practiced over the world. The effectiveness of Tai Chi on postural control and balance has been described in older population, but until recently there are no studies that include patients with chronic ankle instability. Objectives: The aim of this study was to evaluate the effectiveness of 12 weeks of Tai Chi intervention on dynamic balance and self-reported instability in patients with chronic ankle instability. Study Design: A randomized controlled trial was carried out. Setting: University physical therapy facility. Participants: Fifty-two participants were allocated to an intervention group (n = 26) based on Tai Chi training or a control group (n = 26) who received no intervention. Intervention: The participants completed 12 weeks of Tai Chi intervention (1 h session/2 times per week) or no intervention in the control group. Main Outcome Measures: Outcome measures included postural control and self-reported instability feeling assessed by the Star Excursion Balance Test and the Cumberland Ankle Instability Tool, respectively. Results: There was observed significant improvement in all Star Excursion Balance Test reach distances (anterior [F = 6.26, P < .01]; posteromedial [F = 9.58, P < .01], and posterolateral [F = 8.42, P < .01]) in the Tai Chi group with no change in the control group (P < .01). The intervention group demonstrated significant improvement on self-reported instability feeling assessed by the Cumberland Ankle Instability Tool questionnaire (F = 21.36, P < .01). Conclusion: The obtained results suggested that 12 weeks of Tai Chi intervention have positive effects on postural control and self-reported instability feeling in patients with chronic ankle instability.