This study aimed to examine the long‐term prediction of well‐being and internalizing symptoms from trajectories of externalizing behavior problems in 921 children from a population‐based sample. We found that a high stable trajectory of externalizing behavior from infancy (age 1.5) to mid‐adolescence (age 14.5) predicted lower scores on life satisfaction and flourishing for both girls and boys (age 18.5). The high stable trajectory also predicted higher levels of depressive symptoms in boys and anxiety symptoms in girls (age 18.5). The findings are noteworthy as they document how a person‐oriented study of externalizing behavior problems starting in infancy can predict well‐being and internalizing in late adolescence. The findings underline the importance of early health promotion and problem intervention efforts.