Although a number of studies have examined the developmental emergence of counterfactual emotions of regret and relief, none of these have used tasks that resemble those used with adolescents and adults, which typically involve risky decision making. We examined the development of the counterfactual emotions of regret and relief in two experiments using a task in which children chose between one of two gambles that varied in risk. In regret trials they always received the best prize from that gamble but were then shown that they would have obtained a better prize had they chosen the alternative gamble, whereas in relief trials the other prize was worse. We compared two methods of measuring regret and relief based on children’s reported emotion on discovering the outcome of the alternative gamble, one in which children judged whether they now felt the same, happier, or sadder on seeing the other prize and one in which children made emotion ratings on a 7-point scale after the other prize was revealed. On both these methods, we found that 6- to 7-year-olds’ and 8- to 9-year-olds’ emotions varied appropriately depending on whether the alternative outcome was better or worse than the prize they had actually obtained, although the former method was more sensitive. Our findings indicate that by at least 6-7 years, children experience the same sorts of counterfactual emotions as adults in risky decision making tasks, and also suggest that such emotions are best measured by asking children to make comparative emotion judgments.