Recent research has shown that infants selectively approach prosocial versus antisocial characters, suggesting that foundations of sociomoral development may be present early in life. Despite this, to date, the mental processes involved in infants' prosocial preferences are poorly understood. To explore a possible role of emotions in early social evaluations, the current studies examined whether four samples of infants and toddlers express different emotional reactions after observing prosocial (giving) versus antisocial (taking) events. Experimentally blind coders rated infants' and toddlers' emotional reactions to prosocial and antisocial interactions from video using a 1- to 7-point Likert scale of negative to positive emotion; reactions were rated as more positive after viewing prosocial compared to antisocial interactions in three of four samples. While the observed effects were small, a single-paper meta-analysis suggests that the findings are robust and stable across age. These results support the possibility that emotional reactions play some role in infants' sociomoral evaluations.