The distribution of attachment styles has been shown to differ between groups of children living with their parents and children placed in alternative care (AC), defined as residential or foster. However, this is the first study in Latin America to explore possible factors affecting the quality of attachment in children living in both residential and foster care. Two groups of children (N=57) were compared: one group living in Residential Homes (RC) and the other in Foster Care (FC) in Chile. Children's, caregivers' and structural factors (e.g., child: caregiver ratios) and their links with attachment styles were investigated. The micro caregiving environment (i.e., the specific individual child caregiver relationship), especially the caregivers' engagement, sensitivity, disciplinary control and affection, as well as some structural factors (i.e., child: caregiver ratios), were linked to attachment security in children. Specifically, better emotional caregiving and lower child-caregiver ratios were associated with higher rates of secure attachment. The association between quality of care (as measured by the HOME inventory) and attachment styles seems to be influenced by caregiver relationships (as measured by CCSERSS). Caregiver relationship factors (i.e., affection, engagement and sensitivity) directly impact the quality of the attachment children establish with them while living in AC. However, the relationships that caregivers establish with children under their care can be facilitated by good quality structural factors, particularly child-caregiver ratios.