It is unclear whether the concepts and findings of the underlying neurobiology of adult psychopathy apply to youths as well. If so, a life span approach to treatment should be taken. Because youths’ brains are still developing, interventions at an early age may be far more effective in the long run. The aim of this systematic review is to examine whether the neurocognitive and neurobiological factors that underlie juvenile psychopathy, and specifically callous–unemotional (CU) traits, are similar to those underlying adult psychopathy. The results show that youths with CU traits show lower levels of prosocial reasoning, lower emotional responsivity, and decreased harm avoidance. Brain imaging studies in youths with CU traits are still rare. Available studies suggest specific neural correlates, such as a reduced response of the amygdala and a weaker functional connectivity between the amygdala and the ventromedial prefrontal cortex. These findings are largely in line with existing theories of adult psychopathy, such as the dual-hormone serotonergic hypothesis and the integrated emotions systems theory. We recommend that future studies investigate the role of oxytocin, invest in the study of neural mechanisms, and study the precursors, risk factors, and correlates of CU traits in early infancy and in longitudinal designs.