A good understanding of a disease facilitates patient-centered management. We aimed to develop and validate a questionnaire to assess inflammatory bowel disease (IBD)-related knowledge and analyze the factors affecting patients’ knowledge of IBD. We invited 15 experts to develop and modify an IBD knowledge questionnaires and 709 patients to test the reliability and validity of the questionnaires as well as analyze the factors related to the disease knowledge of patients with IBD. In internal consistency, Cronbach’s α coefficients for the common items, ulcerative colitis (UC), and Crohn’s disease (CD) knowledge questionnaires were 0.886, 0.89, and 0.886, respectively. In cross-item consistency, Spearman-Brown split coefficients of the common items, UC, and CD knowledge questionnaires were 0.843, 0.812, and 0.812, respectively. In time consistency, the test-retest reliability ICC was 0.862 (P < 0.001). The correlation between researcher scores, IBD-KNOW scores, and the original questionnaire scores was greater than 0.7 (P < 0.001). Multiple linear regression demonstrated that the factors, including disease type, age, body mass index, education level, income, treatment cost, duration of disease, and frequency of visits, affected the IBD patients' knowledge of the disease (P < 0.05). The IBD knowledge questionnaires had good reliability and validity and, therefore, can be used to assess patient knowledge of the disease.© 2023. The Author(s).