Background Breastfeeding rates for United States women with lower incomes fall below the government’s Healthy People 2020 Goals. Breastfeeding recommendations combined with support from providers and peer counselors help women decide to begin and sustain breastfeeding, but peer counselor uptake is low. Research Aim To evaluate changes in referrals to Women, Infants, and Children’s Supplemental Nutrition Program peer counselors, reported prenatal provider education and support, and breastfeeding outcomes (intention, initiation, 1-month duration of any and exclusive breastfeeding) after a prenatal breastfeeding promotion intervention. Method In this pre-post intervention study (2015–2016; upstate New York), providers implemented a Toolkit to discuss infant feeding recommendations and initiate peer counselor referral. We surveyed women pre- and post-implementation (after delivery; 1 month postpartum) about prenatal breastfeeding intentions, provider support, and breastfeeding outcomes. Analyses controlled for secular trends. Results Pre-intervention ( n = 71) and post-intervention ( n = 70) participants were 49% Black, 61% publicly insured, and 16% uninsured. More post-intervention participants had > 1 Toolkit use (76%), peer counselor program referrals (60.0% post vs. 36.6% pre, p < .01), reported any breastfeeding intention (89% vs. 72%, p = .013), and intended to breastfeed for > 1 year (31% vs. 14%, p = .014). Post-intervention breastfeeding initiation and exclusivity were higher, but not significantly different. Post-intervention participants reported better prenatal breastfeeding support. Conclusions Implementing a prenatal Breastfeeding Toolkit, including facilitating peer counselor referral, was associated with increases in provider counseling, participants’ breastfeeding intentions, and uptake of peer counselors. Replicating this approach may reinforce efforts to support breastfeeding in similar practices serving women with lower incomes.