BACKGROUND: A randomized trial was conducted to investigate the effects of computerized cognitive training (CCT) and tai chi exercise (TCE) vs. health education (HE) on cognitive functions in 189 older adults with mild cognitive impairment (MCI). METHODS: Cognitive functions were assessed by the five-domain Mattis Dementia Rating Scale (MDRS) (attention, initiation/perseveration, construction, conceptualization, and memory) and the modified Telephone Interview of Cognitive Status (TICS-M), while the timed up and go (TUG), Tinetti's balance, activities of daily living (ADLs), and Activities-specific Balance Confidence (ABC) were also evaluated. Each intervention was delivered once a week for 6 months. All outcomes were followed up at 6 and 12 months of the study. RESULTS: Compared to HE, CCT increased scores on the MDRS's total, initiation/perseveration, construction, and conceptualization domains and on the TICS-M at 6 months and those on the MDRS's total, attention, construction, conceptualization, and memory domains and on the TICS-M at 12 months; TCE increased scores on the MDRS's total and construction domains and on the TICS-M at 6 months and those on the MDRS's total, attention, initiation/perseveration, and conceptualization domains and on the TICS-M at 12 months. Moreover, CCT improved the TUG at 6 and 12 months and Tinetti's balance at 12 months, and TCE improved the TUG at 6 and 12 months, Tinetti's balance, and ABC at 6 and 12 months, and ADLs at 12 months. CONCLUSIONS: The effects of CCT and TCE on improving global cognition and certain cognitive domains for older MCI adults may have been small but they lasted for at least 12 months.