Three experiments examined children’s ability to feel regret following a failure to act prosocially. In Experiment 1, 90 6-to 7-year-olds and 107 7-to 9-year-olds were given a choice to donate a resource to another child. If they failed to donate, they discovered that this meant the other child could not win a prize. Children in both age groups then showed evidence of experiencing regret, although not in control conditions where they had not made the choice themselves or their choice did not negatively affect the other child. In Experiment 2, 85 5-to 6-year-olds and 109 7-to 9-year-olds completed the same task; only the older group showed evidence of regret. In Experiment 3, with 134 6-to 7-year-olds, experiencing regret was associated with subsequently making other prosocial choices.