This study focuses on the relationship between belief in a just world (BJW) and the feelings and behavior of young prisoners, taking into account their familial background and criminal career. Our sample comprised 66 young male prisoners from a German detention center. Regression analysis provided evidence for the three functions of the BJW: (a) High believers showed more justice motive-congruent behavior, e.g., they revealed fewer disciplinary problems during imprisonment. (b) High believers interpreted events in their life as more just, e.g., they perceived their legal proceedings as more just; consequently, they reported more feelings of guilt, and they were better able to cope with their anger. (c) High believers revealed more trust in their future, e.g., they were more confident that they would be able to achieve their personal goals. Overall, the BJW seems to be an important resource capable of improving young prisoners’ rehabilitation prospects.