This quasi-experimental embedded mixed-methods study evaluated the effect of a prenatal shared decision-making (SDM) counseling session on decisional conflict and breastfeeding performance among primiparous women in Zahedan, Iran. A total of 112 pregnant women at 35-37 weeks' gestation were allocated to either an intervention group receiving one 90-minute SDM counseling session or a control group receiving routine prenatal care. Decisional conflict was assessed at baseline, one week post-intervention, and three days postpartum. Breastfeeding performance was evaluated on days 3 and 60 postpartum.