Researchers have recently shown that regret functions to lead appropriate behaviors not to repeat the same failure again. Previous studies also argued that emotions have "functions of expression" in addition to such "functions of experience," but how expressing regret functions has not been sufficiently investigated. In the present article, we first reviewed the relations across remorse, guilt, and regret, and then reexamined a hypothesis suggested by Van Kleef et al. (2006) that expressing interpersonal regret signals future behavioral change and interpersonal sensitivity, and thus facilitates the construction of relationships. Supporting our predictions, the results showed that persons who indicated interpersonal regret were more likely to be judged trustworthy and were more desired as partners than persons who did not. We discuss the functions of experiencing and expressing regret.