The aim of this study was to investigate the relationship between intolerance of uncertainty (IU) and mental health in patients with Inflammatory Bowel Disease (IBD), and to explore the mediating role of coping styles. A questionnaire was administered to adult patients with IBD, which included general demographic information, the Intolerance of Uncertainty Scale, the Generalized Anxiety Disorder-7, and the Patient Health Questionnaire-9. The study ultimately included validated questionnaires from 163 IBD patients. Intolerance of uncertainty was significantly and positively correlated with anxiety (r = 0.738, p <
0.01) and depression (r = 0.683, p <
0.01). The mediating effect of adaptive coping style was not significant. The maladaptive coping style partially mediated the relationship between IU and anxiety, as well as between IU and depression, with the mediating effect size of 25.5% and 34.2%, respectively. Our findings emphasize the impact of the inability to tolerate uncertainty on the mental health of patients with IBD. It suggests that interventions can be implemented to enhance IBD patients' tolerance of uncertainty and to modify their maladaptive coping styles to promote mental health. This offers a valuable framework for psychological interventions for IBD patients.