People's risk perceptions can have powerful effects on their outcomes, yet little is known about how people respond to risk information that disconfirms a prior expectation. We experimentally examined the affective, cognitive, and behavioral consequences of expectation disconfirmation in the context of risk perceptions. Participants were randomly assigned and then prompted toward either a high or low personal risk estimate regarding a fictitious health threat. All participants then received the same risk feedback, which presented either a negative disconfirmation experience (i.e., worse than expected) in the high-risk estimate condition or a positive disconfirmation experience (i.e., better than expected) in the low-risk estimate condition. Participants who experienced the negative disconfirmation reported stronger intentions to prevent the threat in the future compared to participants who experienced the positive disconfirmation. This effect was mediated by both disappointment about the risk feedback and perceptions of the severity of the threat. These findings have implications for risk communication, suggesting that the provision of objective risk information may improve or diminish the likelihood of behavior change depending on people's initial expectations and their emotional and cognitive reactions to the information.