Purpose: This study was performed to quantitatively verify the relationships among the“trust state” of patients with type 2 diabetes, recognition of disease uncertainty, and selfcarebehavior.Method: The present study based on Mishel’s theory of uncertainty in illness had a crosssectionalsurvey design. A questionnaire was developed to identify the state of trust. Thestudy population consisted of adults with type 2 diabetes. A total of 204 questionnaireswere distributed, and 125 completed questionnaires were recovered (response rate 61%).Participants had an average age of 53.6 (SD 9.6) years and included 71 men (62.8%) and42 women (37.2%). State of trust, awareness of disease uncertainty, and self-care behaviorwere evaluated using the questionnaire. To classify the state of trust, the factor structurewas confirmed by exploratory factor analysis of the state-of-trust questionnaire. One-wayanalysis of variance and multiple comparisons were used to examine each relationship.Results: The number of items in the state of trust questionnaire was changed from tento six. As a result of the promax rotation of the main factor method, the following threefactors were extracted: “wants compatible doctors,” “trusts doctor easily,” and “receivemedical care at one’s own convenience.” Cluster analysis using factor scores of six itemsand three subscales from the state of trust questionnaire created four clusters. Thenumbers of participants per cluster were as follows: cluster 1 (high scores for “wantscompatible doctors” and “trusts doctors easily”), 22 (19%); cluster 2 (low scores for“wants compatible doctors,” “trusts doctors easily,” and “receive medical care at one’sown convenience”), 18 (16%); cluster 3, (low score for “wants compatible doctors,” butnot for “trusts doctors easily”), 21 (19%); cluster 4 (lower score for “trusts doctors easily”than “wants compatible doctors”), 52 (46%). For each of the four clusters for the state oftrust, the mean total score of uncertainty in illness perception was not equally distributed.Therefore, Welch’s test was performed, which revealed significant differences in self-carebehavior and meals between clusters 1 and 4 (p < 0.0001).Conclusion: The high rate of meals in cluster 1 suggested that creating a state of trust, i.e.,“wants compatible doctors” and “trusts doctors easily,” is important in nursing. Educationfor diabetes patients should consider their state of trust