Introduction: About 1 in 3 American adults have cardiovascular disease associated with risk factors such as physical inactivity, obesity, and stress. Heart rate variability (HRV) analysis is considered a non-invasive procedure for analyzing cardiovascular autonomic influence. Depressed HRV has been linked to abnormal cardiovascular autonomic modulation. Purpose: This study evaluated the effect of Tai Chi (TC) on cardiac autonomic modulation in healthy adults with experience in TC practice. Design: 10 healthy adults, 7 females and 3 males, with an average age of 53.09 ± 7 yr were included in this study. They were asked not to consume any alcoholic or caffeinated beverages at least 24 hours before the study. Each subject practiced TC for 1 hour. HRV measurements were obtained at supine rest using Nexus biofeedback device before and after 10 min, 20 min and 30 min post TC exercise. Results: The cardiac autonomic function was assessed using frequency domain HRV analyses. Using repeated measures ANOVA and paired t-test, we found that the normalized high frequency power increased significantly from 43.02 ± 12.40% to 52.70 ± 13.20% after 30 min post TC exercise (p<0.05). In contrast, normalized low frequency power decreased significantly from 56.97 ± 12.40% to 47.29 ± 13.20% after 30 min post TC exercise (p<0.05). Conclusion: TC exercise can modulate cardiac autonomic tone by enhancing the parasympathetic activity and reducing the sympathetic activity. Long-term beneficial effects of TC on cardiac autonomic function needs further investigation.