<p>Belief in a just world has been widely regarded as a psychological factor that supports adolescent adjustment. However, prior research has primarily relied on cross-sectional designs and has seldom explored longitudinal temporal relations, particularly how emotional and behavioral difficulties might influence, and be influenced by, belief in a just world. This four-wave longitudinal study investigated the bidirectional associations between both personal and general belief in a just world and internalizing and externalizing problems among Chinese secondary vocational school students, a group facing unique academic and social risks. Participants included 3312 secondary vocational school students (41.5 percent female; average age at baseline = 15.71 years, standard deviation = 0.86), with data collected across four waves at six-month intervals. Random intercept cross-lagged panel models revealed robust reciprocal associations between personal belief in a just world and internalizing or externalizing problems. While general belief in a just world did not significantly predict internalizing problems, internalizing problems significantly predicted a decline in general belief in a just world. Externalizing problems significantly predicted subsequent declines in general belief in a just world. General belief in a just world predicted lower externalizing problems only from Time 3 to Time 4, suggesting a possible age-related effect. These findings underscore the developmental significance of belief in a just world as both a protective factor and a belief system that can be shaped by adolescents’ emotional and behavioral functioning in educational contexts marked by disadvantage.</p>