Emotions form the foundation of infants' early social interactions and yet their role in prosocial behaviors is generally limited to situations of distress and other negative emotions. The present article argues that both positive emotions and the emotion of interest play important roles in prosocial behavior and development. First, we explore the ways in which positive emotions characterize infants' everyday prosocial behavior and the relationships that support these behaviors. We then examine the emotion of interest and its role in infants' prosocial behavior. This article synthesizes recent research on positive emotions in early prosocial development and provides a first attempt to link the emotion of interest to prosocial behavior. We close by discussing future directions for research on prosocial behavior with these emotions.