["Journal of Personality, Volume 94, Issue 2, Page 252-263, April 2026. ", "\nABSTRACT\n\nObjective\nBelief in a just world refers to a personal belief regarding justice and serves adaptive functions in adolescent development. Previous research has mainly focused on the outcome variables of belief in a just world, such as psychological and behavioral responses related to injustice, while the predictors and mechanisms underlying its longitudinal development remain underexplored. Based on cognitive schema theory, justice capital theory, and life history theory, this study aimed to investigate the predictive role of childhood stressful environments—specifically, childhood harshness and unpredictability—and the mediating effect of discrimination perception on belief in a just world.\n\n\nMethod\nA three‐wave longitudinal study was conducted with 515 high school students in southeast China (Mage at Time 1 = 17.20, SDage = 0.46; 45.54% women).\n\n\nResults\nResults showed that the childhood harshness negatively predicted belief in a just world, whereas childhood unpredictability was not significantly associated with it. Additionally, personal discrimination perception, rather than group discrimination perception, mediated the longitudinal relationship between childhood harshness and belief in a just world.\n\n\nConclusions\nThis study offers a perspective focusing on individuals' former experiences for future research on the predictors of belief in a just world, highlighting how childhood adversity can shape perceptions of injustice during adolescence and jointly influence belief in a just world.\n\n"]