The importance of supportive relationships for new parents has been the focus of both research and parenting interventions. Attachment style, typically viewed as a relatively stable trait reflecting one’s comfort in social relationships, as well as social support, or one’s perception of the social context, have both been found to be important for fostering engaged, involved parenting. Less is known, however, about how these variables work together to influence parenting behavior, especially in families at higher risk for negative child outcomes. Data were collected from 152 urban, predominantly African American, low-income parents when their children were 14 and 36 months of age. Results suggest that parents with more social support show greater increases in the frequency of positive parent–child activities over time, but that this effect is mediated by mothers’ attachment style, specifically, their level of anxious/ambivalent attachment. Mothers with more social support tended to be less anxious/ambivalent about close relationships, and this in turn led to increases over time in the frequency of parent–child interactions. Mothers’ tendency to avoid close relationships, however, while correlated with social support, was unrelated to changes in parenting behavior. Implications of these findings for program development, parenting, and the malleability of attachment style based on social context are discussed.