Individual development and aging are shaped by historical changes in sociocultural contexts. Studies indicate that later-born cohorts experience improvements in well-being in the young-old. However, whether this historical trend holds in the old-old remains unknown. Using longitudinal data of Japanese older adults, we examined birth cohort differences in trajectories of well-being as measured by life satisfaction. Data were derived from a nationally representative study conducted from 1987 to 2012. We compared earlier- and later-born cohorts over 10 years in two age groups: the young-old (n = 1,195 per cohort; age 63-74; years of birth: 1913-1924 and 1925-1936) and the old-old (n = 436 per cohort; age 75-86; years of birth: 1901-1912 and 1913-1924). To control for covariates, we used case-matched cohorts based on age and sex. Growth curve models were employed to estimate age-related changes in life satisfaction by age group. At age 75 years, life satisfaction was higher in the later-born cohort than in the earlier-born cohort across age groups. Cohort differences in the rate of change in life satisfaction were absent among the young-old. Among the old-old, the later-born cohort showed steeper declines than the earlier-born cohort. Socioeconomic, social, and health resources did not fully explain the cohort differences in both age groups. Our results suggest that historical improvements in well-being in the young-old do not persist into the old-old. Societal advancements may enable later-born cohorts to survive with limited resources. (PsycInfo Database Record (c) 2023 APA, all rights reserved).