Early adverse rearing environments, in which children experience varying degrees of neglect, deprive the developing brain from experience-expectant caregiving mechanisms that facilitate the development of neural and physiological systems underlying emotional functioning. Caregiver neglect also denies children important social interactions needed to acquire behavioral skills that support emotional competence. Although further work in this area is still needed, our knowledge regarding the association between early deprivation and children’s emotional development has grown considerably in the last decade. In this chapter, we first discuss animal models that support developmental theories underscoring the importance of the caregiver–infant relationship for emotional development. We then acknowledge how varying degrees of neglect may be differentially associated with subsequent emotional outcomes. Finally, we review empirical work in this area from a developmental perspective by addressing how early neglect may impact the development of biological and behavioral mechanisms that underlie emotional functioning across multiple developmental periods.