This study aims to adapt and evaluate the effectiveness of an attachment-based, protective-preventive intervention program implemented by nurses in Family Health Centers (FHC) that routinely follow up infants' health. Attachment-based parenting intervention programs have been developed and implemented in Western countries given that parental sensitivity and secure attachment relationship in the early years are critical precursors of psychological resilience. These evidence-based programs have been widely shown to reinforce responsive parenting behaviors and improve attachment quality. A few attachment-based programs have been adopted in Turkey with documented positive effects. However, adaptations of such programs within the primary healthcare services that actively reach families have yet to be conducted to evaluate their potential widespread use for public benefit. In this proposed project, effective application methods of attachment-based programs identified in previous studies, will be integrated to the current well-child care visits in FHCs. It is expected that this program will positively affect maternal sensitivity, caregiving competence, positive discipline methods, mother-child attachment security, and reduce child problem behaviors (e.g., internalizing and externalizing problems). It is also expected that the program effectiveness will be more robust among mothers from socioeconomically disadvantaged families, those with initially low levels of sensitivity, and anxious attachment pattern. To test these expectations with a randomized controlled trial, 120 mothers with 9-month-old babies from FHCs in Istanbul will participate. Selected FHCs will be randomly assigned to intervention and control conditions. Mother-infant dyads will be divided into intervention (N = 60) and control (N = 60) groups. Following a comprehensive training, nurses will apply five modules with sensitivity and positive discipline themes, including a booster module, to the mother-infant dyads during well-child care visits at the 9th, 12th, 13th, 14th and 15th months following the pretest measurements. The application will draw on nurses' positive feedback to mothers utilizing short video recordings and in-the-moment mother-baby interactions consistent with each module theme. Additionaly, mothers will be exposed to the reminders (e.g., pictures, posters, short film screenings) reflecting maternal sensitivity and secure attachment in the waiting rooms of the intervention FHCs. The proposed project will be carried out by experts from psychology with research and experience in attachment-based intervention in collaboration with the experts working in family medicine, nursing, and primary healthcare. To examine program effectiveness, pretest, posttest, and follow-up measurements will occur at pre-defined times through home visits to mothers. Data on mother and infant demographics and psychological characteristics will be collected using multimethod measurement in line with the program goals. Thus, maternal sensitivity level will be assessed using the Ainsworth Sensitivity Scale and Maternal Sensitivity Q-Sort, and the mother-infant attachment quality will be assessed using the short form of the Attachment Q-Sort. Besides observation, mother-reported sensitivity and attitudes towards discipline, caregiving competence, mental processes underlying child's emotions and behaviors, and psychological characteristics (e.g., adult attachment pattern, depressive symptoms) will be evaluated with widely used measurement tools. Finally, infant development and temperament will be assessed via mother report. Following the intervention program, training will also be given to nurses in the control FHCs, who will deliver a condensed maternal sensitivity program to control mothers. The program will be disseminated to relevant experts and institutions, including the priority stakeholders in the family primary healthcare system. If the program's effectiveness is demonstrated, special efforts will be made to scale-up the program. Given that attachment-based early intervention programs positively affect child development throughout life, improve the family environment and social relations and reduce public expenditure on health problems in the long run, the proposed program is expected to create a similar impact in Turkey and lead to positive psychosocial change.