This paper reviews the current literature on the symptomatology and underlying psychosocial mechanisms for developing callous-unemotional (CU) traits across childhood and adolescence. CU traits include a lack of empathy, interpersonal callousness, and restricted affection. As much research has posited its crucial relatedness to multiple psychopathologies, including antisocial personality disorder, there is a pressing need for a more sophisticated understanding of the etiology, enabling the development of early interventions for CU traits. The current paper considers three aspects in its contribution to the etiology of CU traits: traumatic life events, parental influences, and interpersonal relationships. Current knowledge suggests that although the direct association between childhood maltreatment and CU traits is evident, many underlying mechanisms remain unknown. Additionally, parent influences may exert influence via insecure attachment relationships between infant and caregiver, affecting the internal working model, and via low childhood anxiety and harsh corporal punishment. The symptomatology of CU traits may also be consolidated by actively seeking to affiliate with deviant peers in school. These actions further reinforce their problematic belief in the social acceptance of aggressive behaviours to solve problems. This paper provides some reference for research in related fields. Future research should further elaborate on the potential implication of gender differences in literature; the psychosocial findings should incorporate the genetic-biological perspective in forming an integrated and coherent understanding of CU traits; and research should continue to address the potentiality in the clinical implication of research findings to develop valuable interventions for relevant psychopathologies.