Early caregiving adversity (e.g., abuse, witnessing domestic violence, caregiver deprivation) has a profound impact on behavior and social-emotional development, as well as causing alterations in corresponding stress physiology (McEwen & Morrison, 2013; Tottenham, 2012). Heightened stress-related symptomatology increases the susceptibility for sensory processing challenges, especially sensory over-responsivity (SOR), an intense overaction to sensory stimuli, in these populations (Wilbarger et al., 2010). Yet, the link between SOR and early caregiving adversity is not well understood. This dissertation aimed to provide evidence for sensory processing challenges and their link with emotion dysregulation and physiological responses in youth with early caregiving adversity. Study 1 investigated sensory processing challenges among two distinct groups (adopted from either foster care or those previously institutionalized in orphanage care) of youth with early caregiving adversity. We examined how broad sensory processing challenges generally, and SOR specifically, was associated with mental health. Results showed that youth with early caregiving adversity show heightened sensory processing challenges, including SOR, that in turn partially influenced elevated mental health symptoms. Study 2 investigated the differences in HR responses to mildly aversive sensory stimuli in youth adopted from foster care (AFC) and nonadopted comparison youth. Particularly, this study investigated how SOR and emotion dysregulation influenced HR responses to sensory stimuli in AFC youth. Results showed that AFC participants with higher parent-reported, and experimenter-observed SOR displayed increased HR responses to sensory stimuli relative to AFC participants with lower SOR. Yet, emotion dysregulation only predicted HR responses to some sensory stimuli, suggesting that this hyper-physiological arousal during aversive sensory stimulation is specific to SOR-related dysregulation. Overall, findings show that sensory processing atypicalities are common in youth with early caregiving adversity and are linked to heightened physiological arousal to sensory stimulation and greater mental health challenges. Study results are discussed in terms of their educational implications.