Prosocial behavior involves attempting to improve others' welfare and plays a central role in cooperative social relationships. Among the manifold processes that contribute to prosocial development is the quality of children's attachment to their caregivers. Often, researchers have investigated the link between secure attachment and broad indices of prosociality. Recent theory and research, however, suggest that children's prosocial behavior is multifaceted, with distinct correlates and developmental trajectories characterizing specific prosocial behaviors. We offer a theoretical model of the role of parent-child attachment in the development of prosocial behavior, first broadly, and then with regard to comforting, sharing, and helping, specifically.Further, we review the empirical work on this topic from infancy through adolescence. Overall, evidence supports an association between secure attachment and prosociality, broadly defined, but results vary across comforting, sharing, and helping. We discuss potential explanations for the findings and outline directions for future research examining the role of attachment in shaping the diversity of prosocial behaviors across development.attachment, emotion regulation, empathy, prosocial behavior, social competence 1 | I NTR OD U CTI ON Prosocial behavior involves voluntary action to improve another's welfare; it encompasses diverse behaviors, such as feeding a hungry child, lending a hand to a stranger, or soothing a distraught friend. Individual differences in prosociality emerge early in life and carry significant implications for social development (e.g., Eisenberg, Fabes, & Spinrad, 2006). Given the importance of prosociality in sustaining cooperative human relationships, substantial research has focused on understanding the factors that contribute to its development. One of the most influential theories of social Social Development. 2017;26:661-678.wileyonlinelibrary.com/journal/sode