The purpose of the present study was to examine the relations of children's emotional and behavioral regulation (as indexed by heart rate variability and coping styles) to their emotional and prosocial responses to a crying infant. Kindergarten and second-grade children's vicarious emotional responses (e.g., facial reactions and heart rate slope) and comforting behaviors were recorded while children heard a crying infant. The mothers of these children completed a measure designed to assess their children's coping responses when exposed to others in distress. It was found that children who were able to regulate their arousal (as assessed with heart rate variance) and typically responded instrumentally when exposed to others' needy states and conditions were relatively unlikely to become distressed and relatively likely to talk to and comfort the crying infant. Compared to boys, girls were found to be more responsive to the crying infant and were reported to engage in more direct, active coping responses when exposed to others in distress. The results are discussed in relation to research on emotion regulation and coping in interpersonal contexts.