Background: Clinical guidelines recommend that patients with long-standing ulcerative colitis (UC) should undergo periodic surveillance colonoscopy. However, the cost and clinical value of performing annual colonoscopy among high-risk patient populations is largely unknown in the Middle East. Therefore, this study aimed to examine the cost and consequence of annual colonoscopy among high-risk UC patients in Saudi Arabia. Methods: A retrospective cohort study was conducted on UC patients who had UC for ≥ 8 years or had primary sclerosing cholangitis (PSC) at any time during their disease,and underwent colonoscopy surveillance between 2010 and 2021 at a university-affiliated tertiary care center. Patients who underwent annual screening were considered adherent, and those who did not were considered non-adherent. The dysplasia detection rate (%) and the costs were expressed in United States Dollars (USD). To generate the 95 % confidence intervals for annual cost and clinical consequence, nonparametric bias-corrected accelerated bootstrapping with 10,000 simulations were conducted. Results: Two-hundred and sixty-one UC patients met the inclusion criteria and were included. Most of the patients 54 % (141 patients), were non-adherent to annual screening, and the patients' mean age and duration of illness were 45 years and 15 years, respectively. The mean annual direct medical costs were USD 10,210.6 for patients who adhered to the annual screening program and USD 6,191.77 for those who did not adhere. The mean rates of dysplasia detection were 1.66 % and 7.09 % for patients who adhered and patients who did not adhere to annual colonoscopy, respectively. The difference in costs and rates of dysplasia detections between those who adhered to the annual screening and those who did not were USD 4,018.88 (95 % CI: 3097.46 - 6,798.06) and -5.43 % (95 % CI: -10.019 - -1.58730), respectively, resulting in an incremental cost-effectiveness ratio (ICER) of USD 740.125 per 1 % reduction in the rates of dysplasia. According to the bootstrap cost effectiveness distributions, adherence to the annual screening for UC patients would result in higher cost and lower rates of dysplasia development with more than 99 % confidence level. Conclusion: Adherence to annual colonoscopy screening detects more dysplasia in UC patients but with an increased cost. Considering the low rate of progression to colorectal cancer among UC patients, the annual screening might not be cost effective.