Recent studies have shown that preterm delivery is a risk factor for the development of postpartum depression, which not only impairs maternal-infant interactions, leading to infant developmental delay and social interaction difficulties in affected children, but also increases the risk of depression in the mother. Hence, this article aims to study the effects of parental engagement and early interactions with preterm infants on subsequent infant development and behavior, maternal adjustment, and mother-infant relationship. A total of 151 infants/mothers were enrolled in our study. Infants were randomized either to receive early parent interaction or standard care. The early parent interaction program was performed in addition to routine standard of care, Kangaroo Mother Care, during the neonatal intensive care unit stay based on PremieStart Protocol. The behavioral competencies of preterm infants were assessed, as were their mothers' adjustment (depression and coping) and competencies (knowledge of child development). At 12 months of postnatal age, child competencies (development and behavior) were assessed, together with maternal adjustment (parenting stress and depression). Mother-infant interaction was also observed. Early parent interaction did not alter early or later infant development. Furthermore, early parent interaction did not alter early maternal adjustment or late mother-infant relationship, but it reduced the risk of late postpartum depression. Taken together, these studies provide a strong basis for interventions that support parents in the parenting role and guide parents in developmentally appropriate interactions with their preterm babies. These interventions have the potential to lessen the adverse impact of preterm birth on babies and mothers. In addition, the positive benefits of reduced stress can improve parent mental health outcomes and ultimately may further improve parents' relationships with their babies.