Background: Peer counseling programs have demonstrated efficacy in improving breastfeeding rates in the low-income population, but there is little research concerning why women enrolled in these programs ultimately discontinue breastfeeding., Objective: This study aimed to describe the self-reported reasons for discontinuing breastfeeding among women who are receiving peer counseling support by participant characteristics and timing of discontinuation., Methods: This study is a secondary analysis of data collected from 7942 participants who discontinued breastfeeding while enrolled in a peer counseling breastfeeding support program from 2005 to 2011. Reasons for discontinuing breastfeeding were assessed in relation to participant characteristics and weaning age using chi-square analyses and Kruskall-Wallis analyses of variance., Results: The most common reasons reported for discontinuing breastfeeding were mother's preference (39%) and low milk supply (21%), although reasons differed by age of infant weaning (P < .001). Among participants who discontinued the earliest, the most commonly cited reasons were breastfeeding challenges [median duration (interquartile range), 4.7 (2.0, 13.4) weeks], followed by low milk supply [8.9 (4.6, 19.1) weeks] and mother's preference [12.9 (5.0, 25.7) weeks]. Women who were younger, were less educated, were non-Hispanic black, were unmarried, and had no prior breastfeeding experience were the most likely to discontinue breastfeeding due to mother's preference., Conclusion: Peer counselors are in a unique position to offer breastfeeding education and encouragement and may be able to use evidence presented here to anticipate specified concerns either prenatally or postpartum, to prevent early breastfeeding discontinuation., (© The Author(s) 2014.)