Posttraumatic stress disorder is associated with increased dementia risk but less is known about stress because of everyday problems in diverse populations. A total of 9605 health care plan members who provided information regarding midlife stressors in 1972 to 1973 (ages, 40 to 55 y) were followed for dementia diagnosis between 1996 and 2017. Cox proportional hazard models evaluated associations between midlife stressors and dementia adjusting for demographics and lifecourse health indicators. Reporting at least 1 midlife stressor was associated with 17% greater dementia risk [hazard ratio (HR), 1.17; 95% confidence interval (CI),1.07-1.27] versus 0 midlife stressors and 26% increased risk among those with less than equal to high school education (HR, 1.26; 95% CI,1.09-1.44) adjusting for demographics. Compared with whites without stressors, whites with ≥1 stressor had 13% greater dementia risk (HR, 1.13; 95% CI, 1.02-1.24), blacks without stressors 19% greater risk (HR, 1.19; 95% CI,1.08-1.32), and blacks with ≥1 stressors 47% greater risk (HR, 1.47; 95% CI,1.27-1.69) in fully adjusted models. Resource problems were associated with 20% greater risk (HR, 1.20; 95% CI, 1.01-1.42) than interpersonal problems. Reporting ≥1 serious midlife stressor was associated with elevated dementia risk, especially stressors related to resources problems and for those with less than equal to high school education. Everyday stressors can impact brain health over the long term and may contribute to racial inequities in dementia rates, though education can be a mitigating factor.