Objective: to compare breastfeeding self-efficacy, parenting behaviors, and adaptation to the maternal role in mothers with planned and unplanned pregnancies during the early postpartum period. Method: a cross-sectional study was conducted with 414 mothers using a convenience sample at a postpartum clinic in a university hospital. Data collection was performed using a form containing sociodemographic and obstetric variables, the Postpartum Parenting Behavior Scale, the Myself as Mother Scale, and the Breastfeeding Self-Efficacy Scale-Short Form. Results: of the 414 mothers included in the study, 163 (39.4%) had unplanned pregnancies. Mothers with unplanned pregnancies had significantly lower breastfeeding self-efficacy, parenting behavior, and maternal role scores than those of mothers with planned pregnancies (p < 0.001). According to regression analysis, unplanned pregnancy is a risk factor that negatively affects mothers’ breastfeeding self-efficacy, parenting behavior, and maternal role (p < 0.001). Conclusion: the self-efficacy in breastfeeding among mothers with unplanned pregnancies was quite low, and their parenting behaviors and maternal roles were quite inadequate. Nurses and midwives should support mothers with unplanned pregnancies in terms of breastfeeding their babies, both during pregnancy and in the early postpartum period, and in adapting to the role of motherhood and raising children.