This longitudinal randomized controlled trial examined the impact of a doula home visiting intervention for young, low-income mothers on parenting and toddler social-emotional development and tested whether intervention effects were moderated by maternal emotional and behavioral health characteristics. 156 mothers were offered home visits from a home visitor starting in mid-pregnancy through several years postpartum, with a community doula also working with the mother during pregnancy and after the birth. 156 received case management. Interviews, video recordings of mother-child interactions, and toddler assessments were conducted at 3 weeks, 3 months, 13 months, and 30 months of age. Intent-to-treat analyses conducted with the full sample showed some intervention effects. Moderation analyses, however, showed that most effects were concentrated among mothers engaged in high levels of risk-taking (delinquent behaviors, school suspensions, smoking, alcohol use, sexual risk-taking). Among higher risk-taking mothers, the intervention was related to less intrusiveness during early infancy, less psychological and physical aggression during toddlerhood, more sensitive parenting attitudes, and greater toddler social relatedness. Maternal depressive symptoms were only a moderator for toddler behavior problems. These findings suggest that doula home visiting may be a particularly effective model for enhancing sensitive, non-aggressive parenting among young mothers with a history of risk-taking behavior.