In this study, we investigated the association between positive emotion expression in children's writing at age 11, as indicated by objective raters, and age 50 self-reported well-being outcomes—positive emotions, optimism, life satisfaction, meaning in life, social well-being, and physical health. Using a representative sample (N = 436) from the United Kingdom who participated in the National Child Development Study (NCDS), we found that positive emotion expression at age 11 was related to greater optimism, life satisfaction, meaning in life, and social well-being, but not positive emotions or physical health, at age 50 after controlling for socioeconomic status (SES) in adulthood. The associations between positive emotion expression in childhood and well-being in adulthood remained significant when accounting for age 11 academic ability and SES. By using an observational measure of positive emotion during childhood and accounting for relationships among well-being outcomes in adulthood, our findings offer important insights regarding the long-term correlates of children's positive emotions. [ABSTRACT FROM AUTHOR]