There remains a dearth of life-course studies analyzing childhood environment and late-life chronic illness. In particular, few have addressed possible early-life predictors of dementia. This study examines relationships between childhood stress and later-age dementia, specifically Alzheimer's disease (AD). We used data from 2682 men in the population-based Kuopio Ischemic Heart Disease Risk Factor Study who participated in extensive baseline health examinations and interviews between 1984 and 1989, when they were between 42 and 61 years of age. Childhood events were documented in these structured interviews. We created a composite childhood stress variable that included living in custody or an orphanage, experience of crisis in childhood, having problems with teachers and emigrating because of war. Data on incident cases of dementia, including AD, were obtained through 2014 via national health register linkages. Risk of developing dementia was estimated using Cox regression adjusting for age, education, income and prior/existing diseases at baseline. Childhood stress was associated with increased risk of dementia (HR = 1.86, 95% CI: 1.12-3.10). Associations remained statistically significant after adjustment for age, education, income and other covariates (HR = 1.93, 95% CI: 1.14-3.25). Associations were marginally significant with AD, with HRs of similar magnitude. Childhood stress plays an important role in late-life dementia risk among men. Support systems should be developed for children suffering from stressful conditions. Further research examining childhood social and environmental effects on later morbidity, in diverse populations, is necessary to develop a holistic understanding of life-course disease burden.