Antisocial behavior is costly and harmful to families, communities, and society. With roots in early childhood, antisocial behavior puts children at risk for poor physical and mental health outcomes across development. Callous–unemotional (CU) traits identify a subgroup of youth with particularly severe and stable antisocial behavior. Although much literature has examined CU traits in late childhood and adolescence, researchers are beginning to elucidate the developmental origins of CU traits. In this article, we review research examining the measurement and correlates of CU behaviors in early childhood, along with evidence that these early behaviors predict later measures of CU traits. We then describe research highlighting the role that parents play in the development of CU behaviors in early childhood. Finally, we outline translational implications and ethical considerations for studying CU behaviors and consider the use of the term CU traits in young children.