Background: Central obesity is a major manifestation of metabolic syndrome, which is a common health problem in middle-aged and older adults. Objective: To examine the therapeutic efficacy of tai chi for management of central obesity. Design: Randomized, controlled, assessor-blinded trial. (ClinicalTrials.gov: NCT03107741) Setting: A single research site in Hong Kong between 27 February 2016 and 28 February 2019. Participants: Adults aged 50 years or older with central obesity. Intervention: 543 participants were randomly assigned in a 1:1:1 ratio to a control group with no exercise intervention (n = 181), conventional exercise consisting of aerobic exercise and strength training (EX group) (n = 181), and a tai chi group (TC group) (n = 181). Interventions lasted 12 weeks. Measurements: Outcomes were assessed at baseline, week 12, and week 38. The primary outcome was waist circumference (WC). Secondary outcomes were body weight; body mass index; high-density lipoprotein cholesterol (HDL-C), triglyceride, and fasting plasma glucose levels; blood pressure; and incidence of remission of central obesity. Results: The adjusted mean difference in WC from baseline to week 12 in the control group was 0.8 cm (95% CI, -4.1 to 5.7 cm). Both intervention groups showed reductions in WC relative to control (adjusted mean differences: TC group vs. control, -1.8 cm [CI, -2.3 to -1.4 cm]; P<0.001; EX group vs. control: -1.3 cm [CI, -1.8 to -0.9 cm]; P<0.001); both intervention groups also showed reductions in body weight (P<0.05) and attenuation of the decrease in HDL-C level relative to the control group. The favorable changes in WC and body weight were maintained in both the TC and EX groups, whereas the beneficial effect on HDL-C was only maintained in the TC group at week 38. Limitations: High attrition and no dietary intervention. Conclusion: Tai chi is an effective approach to reduce WC in adults with central obesity aged 50 years or older.