Background: The purpose of this study was to investigate the effect of circuit training on β-amyloid, BDNF, and cognitive function in untrained obese elderly Korean women. Methods: The subjects for the study were aged 65–70 years and were each assigned to a circuit training group (EG, n = 12) or a control group (CG, n = 11). The 60 min combined exercise was performed 3 times per week for 16 weeks. The exercise intensity was progressively increased from a 40% heart rate reserve to a 70% heart rate reserve. The test data were analyzed using a paired t-test, an independent t-test, and a two-way repeated measures ANOVA, and an alpha level of 0.05 was set for all tests of significance. Results: Group-by-time interaction effects were observed for β-amyloid (p < 0.05), brain-derived neurotrophic factor (p < 0.01), and cognitive function (p < 0.05). Within the exercise group, significant differences were found in β-amyloid (p < 0.05), brain-derived neurotrophic factor (p < 0.001), and cognitive function (p < 0.05) when comparing across different time points. Additionally, there were statistically significant differences between groups in post-exercise β-amyloid (p < 0.05), change in β-amyloid (p < 0.05), brain-derived neurotrophic factor (p < 0.01), and cognitive function (p < 0.05). Conclusions: Therefore, it is suggested that the circuit training used in this study could be an effective exercise method for improving the risk factors of cognitive impairment in obese elderly Korean women.