Objective The purpose of this study was to compare breastfeeding duration in mothers after delivery who were assigned randomly to a behavioral educational intervention vs enhanced usual care. Study Design We conducted a randomized trial. Self-identified black and Latina mothers early after delivery were assigned randomly to receive a behavioral educational intervention or enhanced usual care. The 2-step intervention aimed to prepare and educate mothers about postpartum symptoms and experiences (including tips on breastfeeding and breast/nipple pain) and to bolster social support and self-management skills. Enhanced usual care participants received a list of community resources and received a 2-week control call. Intention-to-treat analyses examined breastfeeding duration (measured in weeks) for up to 6 months of observation. This study was registered with clinicaltrial.gov ( NCT01312883 ). Results Five hundred forty mothers were assigned randomly to the intervention (n = 270) vs control subjects (n = 270). Mean age was 28 years (range, 18–46 years); 62% of the women were Latina, and 38% were black. Baseline sociodemographic, clinical, psychosocial, and breastfeeding characteristics were similar among intervention vs control subjects. Mothers in the intervention arm breastfed for a longer duration than did the control subjects (median, 12.0 vs 6.5 weeks, respectively; P  = .02) Mothers in the intervention arm were less likely to quit breastfeeding over the first 6 months after delivery (hazard ratio, 0.79; 95% confidence interval, 0.65–0.97). Conclusion A behavioral educational intervention increased breastfeeding duration among low-income, self-identified black and Latina mothers during the 6-month postpartum period.