Objectives: To assess whether a telephone-based breastfeeding intervention delivered by lactation educators influenced exclusive breastfeeding rates among low-income Hispanic women in the USA. Design: Randomised two-group design. Setting: Pregnant low-income Hispanic women (298) were recruited from community health clinics in Los Angeles County (USA) and randomly assigned to either a control or an intervention group. Methods: Data relating to the factors associated with breastfeeding were collected during the third trimester. Breastfeeding outcome data were collected at 72 hours, 1 month, 3 months and 6 months postpartum. Results: There were no differences between the groups in rates of breastfeeding initiation. There was a significant difference in the duration of exclusive breastfeeding among participants during the infant's first week of life. While not significant, after controlling for covariates and intent to breastfeed at third trimester, the duration of exclusive breastfeeding among all participants was, on average, longer for intervention group mothers than control group mothers. Additionally, the intervention group mothers were more likely to report exclusive and only breastfeeding at all data points compared to the control group and less likely to discontinue breastfeeding. Conclusion: Findings from this study suggest that telephone-based breastfeeding interventions delivered by a lactation educator show promise as a cost-effective strategy for improving both the quantity and the duration of breastfeeding among low-income Hispanic women in the USA. Intervention group mothers not only sustained breastfeeding for a longer durations but also provided their infants with greater amounts of breast milk over these longer durations.