An umbrella review of systematic reviews and meta-analyses of randomized controlled trials (RCTs) was conducted to evaluate the existing evidence of Tai Chi as a mind-body exercise for chronic illness management. MEDLINE/PubMed and Embase databases were searched from inception until March 31, 2019, for meta-analyses of at least two RCTs that investigated health outcomes associated with Tai Chi intervention. Evidence of significant outcomes (P value < 0.05) was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system. This review identified 45 meta-analyses of RCTs and calculated 142 summary estimates among adults living with 16 types of chronic illnesses. Statistically significant results (P value < 0.05) were identified for 81 of the 142 outcomes (57.0%), of which 45 estimates presenting 30 unique outcomes across 14 chronic illnesses were supported by high (n = 1) or moderate (n = 44) evidence. Moderate evidence suggests that Tai Chi intervention improved physical functions and disease-specific outcomes compared with nonactive controls and improved cardiorespiratory fitness compared with active controls among adults with diverse chronic illnesses. Between-study heterogeneity and publication bias were observed in some meta-analyses.