Cognitive decline in older adults is a major public health problem and can compromise independence and quality of life. Exercise and diet have been studied independently and have shown to be beneficial for cognitive function, however, a combined Tai Chi, resistance training, and diet intervention and its influence on cognitive function has not been undertaken. The current study used a 12-week non-randomized research design with experiment and control groups to examine the effect of a combined Tai Chi, resistance training, and diet intervention on cognitive function in 25 older obese women. Results revealed improvements in domain specific cognitive function in our sample. Baseline cognitive function was correlated with changes in dietary quality. These findings suggest that Tai Chi and resistance training combined with diet intervention might be beneficial for community-based programs aiming to improve cognitive function.