Doctor-patient communication interacts with patients' satisfaction to influence patients' risk perception. Current theories to explain this relationship have assumed particular psychological processes to explain observations of risk-sensitive behavior in an economic setting, but as of yet, they have not addressed whether it is adaptive for a decision-maker in a health-care situation. In addition, little is known about the role of interpersonal trust between doctor and patient. We surveyed 602 patients to examine the way in which trust, communication, and patients' satisfaction are related to patients' risk perception about uncertainties in medical treatment. The results showed that patients held a relatively low level of risk perception, which means that they had insufficient preparation for the possibility of uncertainties about the treatment. The association between doctor-patient communication and patients' perceived risk was mediated by doctor-patient trust. These results suggest that there is a relationship among good doctor-patient communication, patients' trust in medical staff, and perceived risk during medical treatment. Finally, theoretical and practical implications are discussed.