This study was designed to test the efficacy of the health promotion program used on maternal-infant attachment, parental self-efficacy, infant development. For this experimental study parallel-group randomised control design was used. Data was collected from 64 mother and their infants. The intervention group received the health promotion program in addition to standard care, the control group received only the standard care. Family Information Form, Prenatal Attachment Inventory, Maternal Attachment Inventory, Parenting Self-Efficacy Scale, and Denver II Developmental Screening Tests were used for the collection of the data. Pearson χ2 test, Yates corrected χ2 test, independent t-test, and Mcnemar test were used for analysing the collected data. The groups on maternal-infant attachment (d:1.20 [CI:0.671–1.736]), parental self-efficacy (d:1.37 [CI:0.835 to 1.925]), and development delays of infants (p =.003, C.V: 0.41) were found to be statistically significant. Health promotion program positively influenced the maternal attachment, parental self-efficacy, the development of the infants.IMPACT STATEMENTWhat is already known on this subject? Pregnancy and postpartum is a difficult period for mothers. Mothers need support. Parenting self-efficacy and maternal attachment are important for improving infant health. Infant should be supported to prevent developmental delays. What do the results of this study add? With the education and support program applied before and after birth, mother and baby were evaluated together and multi-faceted support was provided. What are the implications of these findings for clinical practice and/or further research? Supporting parenting self-efficacy, maternal attachment and infant development should be started during pregnancy and should be continued in the postpartum period.